I'm 22 years old and I've been married two years now. We have an 8 month old baby and have a pretty good relationship. So, while I was pregnant, he said to me that he had been tempted to look at porn one day while he was stressed out. Now he has a past way before me where he looked at it quite a bit but he stopped cold turkey a year before he met me. It struck me that this was the first time he had been really tempted and me being heavily pregnant. I am completely open to having sex with him anytime anywhere so I asked him why he didn't just come to me as I would have even been happy to have sex with him and he knows this. He said,'it's a man thing and you wouldn't understand'. So he didn't do it and no problem there but it planted a seed of jealousy in me and it's been slowly growing out of hand. I wondered was it me being pregnant and was I ugly when I was pregnant and was that why? It made me wonder will I be unattractive to him every time I become pregnant? He assured me that this wasn't the case. Fast forward to now - we get into a discussion about men who check out women on the street. I say, "Why do people do that? It's so bad aren't they satisfied with the girl they are with." He responds,"well, I think all men do it without meaning to." What is that?! So, I ask him if he has done it or even recently. Yes and yes to all questions, but he clarifies that because women are dressed so skimpily these days it's an automatic glance and he doesn't indulge it or even think about it for too long so I shouldn't be upset. But I am - really upset. It tortures me that he would find anyone else attractive even without meaning to and it really eats me up. I find myself looking at other women really uncharitably if I suspect that they are decently pretty or not dressed well. It makes ME feel like dressing slutty to compete with them in an irrational way. I've never had body issues or anything like that before. I know that (Not to be vain, just giving context) I am a very attractive person even after giving birth. There is actually no reason why I should be jealous but somehow I can't believe him 
anymore when he tells me I am pretty or rather that': not good enough. I want to be the Prettiest to him. As a catholic, I know that this is not very good for me and my marriage that I feel so bitter and jealous. But isn't it normal to want my husband to not even see any other woman? Or is that crazy? I am even dreading the beach now because I don't know if he will notice the other women or how many 😖 Has anyone gone through this?

"There is actually no reason why I should be jealous but somehow I can't believe him
anymore when he tells me I am pretty or rather that': not good enough."

I don't think you should consider it to be about all about attractiveness. Look at celebrities who are married to women who are considered the gold-standard of beauty, yet they cheat on them constantly. Men often have flings wherein  the mistress would be considered less attractive than their spouse.

It's difficult to dominate a vice one has given free reign to for a prolonged time. At least he is trying. Pray for him. Also some fellowship with good Catholic men for whom this is not the norm ( looking at porn, objectifying women) would probably be helpful.

I wasn't going to post but since the above three posts didn't answer your question I thought I would. Your husband is completely right. This may be hard for a woman to understand, but a man doesn't just stop being attracted to other women once he marries. He will continue notice the attractive women around him. You husband said it's just an automatic glance and he doesn't indulge in it. As you know, a temptation isn't a sin. You should also know that men can be tempted to look at porn at one stage or another, regardless of whether they've had a past. Again, this is not a sin. Now the fact that your husband has a past with it may mean that he's more prone to these temptations, but not necessarily. So to answer you're question there's nothing to be jealous about. The fact that your husband notices other attractive women doesn't mean that he doesn't find you attractive. And while it's perhaps normal to wish your husband wouldn't find any other woman attractive, this is not realistic. You'd never find a husband that would satisfy this requirement. So try to relax, be happy, and accept those compliments your husband gives you. 

Be sure that he understands "lust" is mortal sin.  

As a reformed chaser of bikini clad young girls for 40 years on the beach, now a father of 5 girls, I say that I have nothing to add to what has been said above, everything you need to know is there. Great job everybody.
If I were to boil it down to a "concentrate", I would say it is that posting above. That "prolonged second look", defined by Matthew above, is the mortal sin of lust. Seeking out pornography is the mortal sin of lust. One must immediately do an act of contrition and vow to go to confession on the first chance.

The wife's husband is spiritually sick if he's going to porn sites or lustfully looking at women, scantily clad or otherwise.

As for the wife and her jealousy, being jealous is a sign of spiritual sickness.  The wife should constantly pray for the good of her husband and for him to remain in a state of Sanctified Grace. 

Consulting a traditional Priest would be the best course of action for this couple. 

 It tortures me that he would find anyone else attractive even without meaning to and it really eats me up. I find myself looking at other women really uncharitably if I suspect that they are decently pretty or not dressed well. It makes ME feel like dressing slutty to compete with them in an irrational way.

This doesn't sound like true jealousy to me; it sounds like the OP, now that she has a child, is very atuned to any possible threat  to her family's well being and survival.  Think mamma bear.

Human nature will have 2 responses to the danger;  look for the cause in yourself or accept no responsibility and lay the blame elsewhere.  The OP is looking at herself too closely.

isn't it normal to want my husband to not even see any other woman? Or is that crazy?

Not at all.
St. Thomas Aquinas writes in Summa Theologica II-II q. 169 a. 2:

Nevertheless a woman may use means to please her husband, lest through despising her he fall into adultery. Hence it is written (1 Cor. 7:34) that the woman "that is married thinketh on the things of the world, how she may please her husband." Wherefore if a married woman adorn herself in order to please her husband she can do this without sin.

I think this would be better discussed in the women's only section.  Older, wiser, women would be the most effective at addressing your insecurities.