I realize you are very young, but, you cannot know what you simply do not know because you are inexperienced. The sex you are having right now is nothing like the sex you will have as you age. Boys his age are totally into sex for themselves and their own agenda, their own self gratification. This is so typical of young lovers.
Your inability to climax on your own, for whatever reason, could be why you are unable to be sexually satisfied by him. It takes so much longer for a female to climax than it does for a male. If you want a more satisfying sex life, you must insist he gives you the attention you need to climax BEFORE he does.
His silly story that he is too tired and exhausted to have sex for a couple of days is RIDICULOUS, unless he has a medical condition. Boys his age are typically ready, willing and able to go for several rounds of sex, for days on end. So, something is either wrong with him or he simply does not want to do what it takes to get you off. Selfish boy.
The ONLY way to change things with him, is to talk to him. You also may want to do more experimenting with yourself, on your own private time, so you can learn what satisfies your sexual urges by learning how to climax. Otherwise, you will forever be unhappy with sexual experiences, regardless of who you are with. Minute men or not.