from experience, ive been in two mixed religion relationships, i'm baha'i and she's muslim..
it didnt work out because my parents were against it, not because of religious differences.. but because of cultural differences. i trust my parents because they have known me all my life, plus while we arent all soo close.. i wouldnt want them to be unhappy while im happy in a relationship.. maybe it was me too who didnt really think the match was right..
but the thing is, you should not fall head over heels for him yet.. it would be wrong to change your religion just for the sake of another guy/gal.. trust me on that one! if i may go on, id say from other religious sources that your relationship with god is personal, it cannot be induced or forced, and is often blinded by love for people or material things.. while you are of two diff religions, imho, you still pray to the same creator. you may decide this and be able to live together like this.. or if he wants you to convert then i think its wrong, you shouldnt convert for the sake of another one you love. if ur mom has a prob with religion, and if what i said makes sense to you, then u should explain it to her the way i did.. or better yet, seek more religious counsel from your catholic church.. (youre anonymous during confessions, remember) good luck!
sorry if that sounded harsh, but it's just my view..