Last time I made a past I was in ruins over a girl I thought i loved. It has been a few years since then and what ppl said helped alot. However a little over a year ago I thought I had truly found my match she was wonderful and we both loved each other. She was the first girl non family wise I had cried in front of we were even engaged. But abt out 2 months ago she broke up with me a week before we were going to move in together.she moved in a friend's brother and I had hope maybe we could work past our issues. But she told me not long after she had feelings for her new roomate and wished to be with him over myself. I had been truly hurt that night she even said she loved him. But a week later when she came over to drop my stuff off she slept with me. I dont really think either of us made a move we both just gave in but non the less she cheated on her new guy with me her ex. She is even coming over to and staying the night. Should I just let something happen again should me and her continue trying to be friends. Should I tell her new guy? Idrk but after this heart break ive also been thinking about making myself "disapear" like I truly tried to be her one and only I dont see a point in continueing

Don't. It's not worth it. It's hard to let go, god do I know. But by doing this, you're going to end up hurting yourself even more. Cut her off. Tell the guy. Move on. Someone who deserves you will come along. Don't waste your time on this girl. (And plus, if she cheated on that guy, there's nothing that would stop her from doing the same to you if you did get back together! Save yourself the future heartache.)

That sounds as a really tough spot to be in. Hang in there!
It does not seem that there is way back from this to healthy relationship with her. So sleeping together will only prolong misery. It sucks. It is also challenging to be friends in such situation too. Friend is someone you can trust to have your back. It does not sound as she can be that for you even when you might have been everything for her. I learned hard way too that giving love unconditionally does not make someone return it to you the same way. Some people are selfish. And hopefully you will find strength to move on and do what is best for you and surround yourself with people who truly care about you.