How do I 19/F 19/F fix my head when it comes to relationships?

Hey everyone, so this might be a very confusing post and I’ve never posted on here before so I’m not quite sure what to expect. This has been bothering me for a while now so I’ve finally decided maybe some strangers can give some advice :) Pretty much, after doing some research i feel like I’ve got some sort of like anxious avoidant attachment style but im not too sure if that’s everything. I can’t keep a relationship and I don’t know why. It’s always me that ends them because my brain tells me I don’t like them anymore. So after feeling like that for a while I break up with them, then a couple months later it hits me and I want them back. But if someone doesn’t like me back or they are giving me a bit of a chase then I have the strongest feelings ever and I become so attached to them. I’m very scared to get hurt as I’ve been cheated on in the past so I don’t know if that has something to do with it? I’m also bisexual and this has happened with a girl and a guy. I just don’t understand why I get so moody when I’m messaging them online. It’s like I just get so unhappy but I also don’t want them to leave me alone. As soon as there’s a mention of a serious commitment I suddenly lose feelings and I don’t know what to do about it or how to help it. I really want to change. Can you guys please help me out here? Thank you.