Big problem, don´t know what to do

Hey guys! So i have this really big problem, and i don´t have a clue about how to handle it, so i hope i can have some pieces of advice from you guys. I´ve been dating a girl for about 3 months. I started to see her while she was still with her boyfriend and i had a big impact on them breaking up. In the beginning dating her was the most amazing feeling i´ve ever had, and i think that she felt the same way. Everything moved on very fast and we got intimate really quick. After the first two weeks it started to get problematic for her, and of course it did, she had just breaking up with her boyfriend. So we decided not to see eachother anymore. That lasted for about a week and then we were back together again and it started to get pretty serious. After that it turned bad again and we decided it was for the best if we didnt see eachother, again. During that time she started dating another guy and she started to get feeling for him as well. This sucked big time for me because ive started to understand that i was in love with her, and i got really sad for a week but then she came back and said that she missed me alot and we started seeing eachother again, while she was still dating this other guy. Now its been like this for a couple of weeks and starts to really eat me up, im really in love with this girl and even if ive just been seeing her for a couple of months ive never felt this strongly for a girl before.

So what shoud i do? Should i keep dating her even if hurts this much and hope that she will forget about that other guy? Or should i just give up on her?

As i said before ive never felt this strongly for a girl before so i want to keep fighting for her, but still it hurts so much, so please guys help me out here.

Your relationship started with her cheating, so it will probably end the same way.

Yeah you´re probably right you know but still its so damn hard to just give it all up, because she means so much to me, and i honestly think no matter how stupid it sounds, that i mean alot to her aswell. So probably i will get hurt either way, but im so confused about if i should keep fighting until the end and until she says that she doesnt have any feelings for me or if i just should give up. I hate giving up you know and im so afraid that i will regret it if i do.