I dont know if im wasting my time or not...?

I'm 17 and i think i want to start looking for a serious relationship. My gf is 15 and im not sure if she is as serious about me as i am about her. I love being with her and she makes me happy. but the main problem is that she is a devout catholic and im not, so if our relationship were to go all the way to marriage she would probably want to get married in a catholic church and im not down for that, or raising my kids as catholics. I really like her but i dont know how far our relationship can actually go. Advice?