One key thing to know (which I think is rarely talked about in relationship counseling) is that there is no universal, singular way to show love. Men and women can differ greatly, though gender is not always a determining factor. In this cas, I can sympathize with your boyfriend a bit. I'm a girl, but honestly have a very kicked up libido, usually equal to that of a guy my age. I therefore, like physical statements of love. I like a lot of kissing and holding and intimacy when the time is appropriate because to me, it shows love and desire. Sex should be sacred and saved for your one and only, and so if I feel ready enough to be physical with someone, its because I love them tremendously. Your boyfriend just may be the same
I always sympathize with you. You may see him as childish because it looks as though he has a mind set on sex all the time like a hormonaly drunken sex-addict. You want to get more serious most likely and advance emotionally rather than physically, correct? So when you want to work on this part of your love life with him, his constant come-ons probably agitate and make you feel he's underminding your seriousness over the development of your relationship.
Those two things being said; you both could be equally in love and just not be communicating your needs to each other. Sexuality and emotional bonding can both coexist in a relationship, theyre supposed to after all! You just need to talk over you intentions and desires and come to a point where you understand each other. So sit down and have a good talk with him. Best wishes!