Boy and his ex

Me and this boy have been talking for a few months but haven’t made anything official however we are quite protective over one another, he has a bad attitude to his education which is a big probeom for me and I’m hoping as I’ve spoke to to him that he will change, however his ex is still trying to get back with him and he seems particularly bothered when I ask him to do something about it, it’s taken two months just for him to tell her not to speak to him anymore and to block her because she was constantly messaging him, out of the respect for his ex we went to a party and I wasn’t all over him however, him and his ex were together the whole night, he says she was following him but she says she felt like he was leading her on, there’s a lot more to this and it’s all confusing, my friends are all telling me different things to do and different ways to react and I don’t know what to do