I need help im going crazy.. please?

If she cheated on you early in the relationship the thing is you either have to get over it or end it with her, regardless of anything else you do that's what it's all going to come down to in the end. It does sound like she is a habitual liar and she will continue to lie to you about many things. I'm not saying people can't change but it's not very common. If you have given her several chances in the past and it's still not working, then chances are it probably won't change much this time at all. Within 7 months the relationship is still fairly new even if you don't feel like it and you have be able to handle things getting worse. Little things that annoy you right now about her (anything at all), will start to annoy you more and more as your relationship goes on. Especially when living together. Is it bad about you obsessing over her cheating and/or her lying about it? Not as bad as you obsessing over this person. She has become your obsession and it isn't healthy. Being upset over her cheating on you even though it was earlier on in the relationship is normal, as well as being upset with her lying about it for so long afterward. Apparently, since you have begged her to tell you the truth, you suspected her of lying in the first place. I suggest asking her for a few days alone to gather your thoughts, chill out, and maybe even consider seeing a counselor if you really want to get your relationship back on track that bad and are really to truly work for it if you decide to give her another chance. DO NOT let yourself fall into a state of deep depression. You can also still kick it with your friends during the time away from her and to gather your thoughts but I don't suggest going clubbing or partying.