So I've been dating this amazing guy for about two years now. I definatly know that I love him.

-There is just one thing that kind of saddens me. I've been to his house once. I've met his dad and brother who are very nice. His grandma likes me as well, it's just his mother that doesn't really like girls.

She had a really bad youth, but I just feel sad that I don't get to bond with his family like he gets to with mine. He's invited me to the movies with him back last summer with him and his grandma, and it turned out that I couldn't go because his parents were and he didn't want his mom to be rude to me.
and then he also asked me recently to go for his birthday, but it also turned out that I didn't get to go because his gramma and mom were the only girls there and he didn't want me to feel awkward. I totally wouldn't.

I just don't know what to do!

Have you sat down and talked this out with your boyfriend? It's important that he understand how you feel about it, afterall it's his family you're worried about, and then you two can hopefully work something out that you're both comfortable with.

normaly its guys who feel this way because of the girlfriend's dad so i can help you just stick around and get to know his mom better even become friends with his mom because she probably thinks what all parents think that the person there child is with isnt the right person for them (i know this from experience) you have to show her that you realy care about him and she'll start to trust you i can garuntee it (even if it does take a long time)