Me and my bf talked about marriage and i want to but how do i kno hes the one?

Im 17 and me and my bf have been dating for about 2 years,but we have been best friends since 4th grade.. I kno everything about him and he knows pretty much knows everything about me. So we just started getting serious last month as in (sex) and nothhing has change but i ask him if he would want to ever marry me just jokin around and he said yes.. Ever since then he told me that he would want to spend the rest of his life with me and that he really wants to get married when we can which is next yr.. But we love each other and hes always there when i need him i can talk to him about anything he makes me happy. He calls me all time and tells me that he loves me , always telling me that im beautiful and loves watching me sleep cause im amazing, I have never felt this way before there are things i cant explain cuz i dont know what words to say. But the thing is he has never been in a serious relationship before and i have but the thing is dont think he knows what hes talkin about cuz for one like i said he has never been in a serious relationship and maybe he thinks im the one cuz he hasnt dated in a while. I think hes the one for me cuz my ex i always wanted to be around and i couldnt be myself at all but with him i dont have to see him all the time for me to kno he misses me because he calls to let me kno or stops by.. We have been through almost anything its like we have been married but we cant stay mad each other for more than an hr we just cant we love being around each other we always have a great time and we are always laughing.. But he dont have a job and sometimes acts immature like getting kicked out of wal-mart when we go. It bugs me but i have talked to him about it… So what i really need help with is that i love this guy and would anything for him but i want to know that he would do the same for me…!! We talked about a baby but want to wait till we get out of high school and start a life then a baby but please help…. thank you