As I recall the ex in question is the guy who continued having sex with the OP, even after they broke up and she took on another boyfriend (who is only 15 years old, while she is an adult at age 18, and they don’t kiss, hold hands or have sex or go on dates or visit with each other outside of church).
Then, although the OP says that the 15 year old boy is her boyfriend (although her description of what she does and does not do with him makes him seem more like a fellow she occasionally sees at church and nothing more) she was still having sexual relations with her ex, but then she decided that she didn’t want to do that anymore, so she gave the ex “his space” But it seems more like the ex was only using her for booty call or Friends With Benefits and now that she doesn’t want to have sex with him anymore, he has no interest in being “just friends” with her.
I think she should re-think what the term boyfriend means, because neither of these guys seems like they are or were boyfriends.
I also agree with @gailcalled that she should spend more time on her school work, and she should talk to a school counselor about both her school work and her unusual ideas about sex and relationships, and the inappropriateness of attempting to date underage boys.