I experienced something like this when I was young. You do not say how old you are (I am in my 40s). I was heartbroken when my first love became focused on sin and began to berate me. I heard "You are going to hell because you are Catholic." He once got really upset with me because I wore pants to his church, but he did not tell me NOT to. It was kind of like a game that made him feel superior, if that makes sense. It was very hard when that relationship ended, but now I am so glad that it did. Love is not about berating and tearing down a person. Christ is not about blame; He is about forgiveness and love. Spirituality should be about strengthening your relationship. Also, ultimatums are never a good sign in relationship.
If this is a serious relationship and you have or want to have children, is his church a place you feel that your children would be happy? With differences in religion, once children are involved, it gets extremely emotional and difficult. They become pawns.
You sound like a lovely, loving woman. You deserve to be cherished and loved by your partner. That is what God wants for you.
BTW: my former boyfriend is now an atheist. I am still a practicing Catholic. I mention this only because I think it is very common for young people (early twenties) to go through extremes as they try to understand their spiritual identity. The problems occur when one person tries to force another to bend to his or her belief. This is why I try always to be very respectful of each person's belief (or non-belief).