First off thanks so much for writing in with this question. I love when we get questions that are specific to a person, but that everyone can relate to. I know I've gone through similar things like this, and I'm sure others have had these same feelings.
I think the other member said it really well when they said "just tell him everything you wrote down." I feel like the best way to get through this situation is to be as honest and open as you can be with your boyfriend. Your heart really seems to be in the right place by letting him hang out with his friends, but your boyfriend also needs to realize that being in a relationship means putting your partner above everything else, and being willing to make sacrifices to make the relationship work. With they way things are right now he might not even know that you are feeling this way, so it's really important that you let him know these feelings, without attacking him for hanging out with his friends.
I think a good solution could be possibly planning things where you can hang out with him and his friends. That way you can kind of kill two birds with one stone. The best solution in my opinion is just talk to him and let him know how you're feeling. I'm sure he'll be understanding as long as you tell him that you're not trying to eliminate his friend time, you just want some time for you two as well. And if you really are as important to him as he says than he will make the changes necessary to make things work.
Hope that helps you think about some other things, and let me know if you ahve any more questions.
Kevin