What should I do???? (about my boyrfriend)?

I have a boyfriend who is 18 and I am 15 and I find him one of the good people in my life. We have been going out for almost 5 months. His past is not the best being that he cheated on girls used them and hurt them, but he changed all that a year ago. We met on facebook from a friend and had an instant connection because we are the same race and have a good sense of humor. Over the months things have gotten worse he does not like to argue so things are never resolved and I am one of those people who is very nice and willing to make others happy always especially him, but I feel like he doesnt really do anything for me but ask for things or he will only do something if it benefits him. I have always settled for less and been through so much with guys and my self esteem and he will say how pretty another girl is and stare and let me know that he checked her out but he always says its a joke but it hurts. He has his good moments but I think he can do way better because I give so much for him to be happy, like I trust him so much no matter how much people who have known him for years tell me he is not good and will cheat on me or has. I am not feeling the care and love I felt in the beginning but just not as important anymore. I want to be happy with him but if Im not important enoug for him to listen to what I have to say then I dont know. Any advice would be helpful and so appreciated.What should I do???? (about my boyrfriend)?
never settle for an asshole. kill him.