I just commited an horrible discusting mortal sin that even in anonymous I m afraid of telling. God would be just by letting me die and suffer. I beg you guys to pray for me.

As the others said, get to confession soon as you can. Always keep your rosary on your person and pray 15 decades minimum every single day - and do not miss a day. Do this, and one of the things you will find out in a short time, is that avoiding the near occasion of sin becomes habit forming.