Fun Kerl 26 minutes ago While your theory is a good one its also possible he lost his powers because of love. In the second movie when hes talking to Doc Ock, ock tells him that "if you keep something as complicated as love locked up, it will make you sick." And if you noticed after he sees Mj meet with another man he looks sad, heartbroken. He cant tell her he loves him and that makes him sick. And that leads to him falling from the sky and having to take the elevator.After he hears she will marry J.Js son he cant crawl up walls, web sling, or see straight.Then he see's a doctor and he tells peter "My diagnosis, its all in your head" So its possible he lost his powers because he became sick from love. (Cheesy i know) but it makes sense since right before he and Mj kissed his spider sense kicked in and he saved himself and Mj. In that moment he was able to express his love and he stopped feeling sick and he could become spiderman again.