Breakup issues

I've been dating this guy for 2 years . I lost my virginity to him and I thought that he would be the only person I'd be with. We broke up a few months ago and we recently started talking again and I slept with him.Ever since I slept with him he has been acting weird towards me. Id hit him up to have convo and he just won't be involved and tell me he's busy. I already had a hard time dealing with our breakup and now because I went back and slept with him I really feel crappy . Should I leave him alone or should I ask him why he led me on and then got uninterested ? please help