You two are both very young. That doesn't mean you don't know what you're doing or where you stand (though alot of people might tell you that). What it does mean is that there are a lot of changes ahead of you. A lot. You'll change, he'll change, your relationship with each other will grow and change, your lives will change, all like crazy.

So your best bet for those changes to be positive things that improve your relationship is to be clear about where you stand. Also, be flexible. You might change your mind about things, he might change his mind about things. But if you both communicate how you're feeling, and you're both flexible and open to doing and trying things for your partner's sake, it may surprise you with the things you get to discover. Maybe he's being submissive because he's young. Maybe he's being submissive because, well, he's submissive. Either way your best bet is to communicate clearly how you feel, listen carefully to how he feels, and then find the right balance between changing yourselves for the better and accepting yourselves for who you are.

You've only been together for four months. So you're still just plain learning about each other. So let him know who you are, clearly, and then listen to who he is, too. That would be step one.

Good luck to you.