My mom wont let me spend the night at my boyfriends house.. ASAP?

Even good teenagers are put into the general category of being "bad" kids just because they are not fully grown yet. However, your mom has pretty steady grounds on which to stand. Teens make poor decisions through hormones and other urges that they don't always use their better judgement over. You're only 15 and have plenty of times to sleep over at your boyfriends house. It's probably not you she doesn't trust its him. Just let this one go and she may grow to trust him better and you'll get your chance then.