Even if he is good looking, getting laid is not necessarily that easy (even though guys brag about getting it). At the young age he is now it is very practical to have a girl available for sex. And you say you aren't good in bed - strange thing to say, you do nothing? better for him and you to get moving, don't know how anyone is continuously and knowingly bad in bed, but oh well.. It's still better than nothing, I don't think you can conclude that he must have feelings for you because "he doesn't have the best time in bed anyway".
He has never taken it further, might be because a) he is not interested in you as a gf/get along with you in that sense and you don't fit into his social circle, b) he doesn't want a relationship.
We don't know which one it is, but it is logical that he wants to keep his options open. Preferably he wants you available for sex whenever and for you not to dedicate your time to other guys. He wants to have his cake and eat it too. And he's not the only guy, many would given the option. It's the perfect situation really, when you're still so young commitment is not really something you consider. You can break it off and go for someone else if you want a relationship or continue this, but if you really do have feelings for him, it will be the path to emotional self-destruction.