I had the same dilemma. Which Mass is True? I asked a Redemptorist priest. I thought I would get an answer. He said to me, when you find out let me know.
I was disappointed. But I decided to go to Our Lady, since she was there with Her Son at His Crucifixion. I also decided to look upon the picture of the apparition of Sr. Lucia in 1927. I understood it was part of the 3rd Secret. I also told Mary that I believe that we are all different, and need to be approached by Her in different ways to help us.
So, I looked at this picture and I saw Mary standing at the Cross. My soul said, this is the Sacrifice of the Mass. Then my soul said, Our Lady can only stand by Truth, only one Mass can be true.
So, when you find the True Mass, you will also be able to stand as Our Lady did. Firm and convicted of the Truth.