Were 16 and we have been together over a year, yes I know were young for sex we have done it a lot and tried a lot of differet things but she doesn't want to do it anymore she won't give me a reason why, I'm afraid she might be cheating, I need some advice.

You two need to sit down & talk this out. Communication is VERY important if you want your relationship to work out. Best of luck

You're 16, you shouldn't even be having sex in the first place so maybe stop having sex. Sex is something two financially stable adults do to create life, start a family and raise a beautiful child. Sex is not an activity for fun, once it becomes an activity it becomes meaningless and pointless, therefore the reason she doesn't want to do it anymore.

Give your head a shake stop thinking with your penis and stop trying to act like an adult. What happens if she gets pregnant? Do you have a good job to fall back on so that you can afford the baby? Don't give me the stupid birth control and condom routine because you can use both of those and still get her pregnant.

You should sit down and think about the consequences of what you're doing, maybe even include your parents in the conversation.