How do I "be myself" in a relationship if people are pressuring me to be someone I'm not?

I’ve found that once I’m in a relationship with someone, people (mostly my family) start pressuring me like crazy…

For example my Grandparents want me to “speak highly of my church”. My parents pressure me to stay a virgin. My cousin Rick just pokes fun at me. I feel obligated to be extra courteous to her and her parents.

I know that they’re my family and they just want to help, but I don’t get how I’m suppose to “be myself” If people are pressuring my to be someone I’m not.

I take relationships seriously and with maturity (or at least try to), so please answer in the same fashion. Also, I’m sorry if some of this didn’t make sense, I’m really tired right now…

Thanks a bunch!
-Joe