I need serious relationship advice please!!!?

Hi, i am 20 years old and my girlfriend is 18. We have been together for 1 year and 7 months. Over this span she has lied to me a lot. When we first started dating she lied to me about her one friend that she had on the internet and i found out. i always asked her why she couldn't tell me and she said she felt stupid. After this happened she had this one friend all along who had a huge crush on her, so i told her she couldn't hangout with him because she was obsessed with her and i didn't want him to make a move on her. ( This is because she had a lot of guy friends who flirted) When this happened she didn't stop but ended up hanging out with him and not telling me. I was really hurt about to break up because i didn't feel like anyone should hangout with someone who likes them especially behind my back. Ever since because she lied and what not i wanted her to be honest with me. She has lied to me and tried making promises and never lived up to them. I feel as though it was my fault though. I feel as though i forced things too quickly. Anyway, that all was in the beg. of our relationship and we were fine for awhile. Of course many lies happened since then, none too extreme but enough to hurt me (like promises she never kept). Just recently she cheated on me with a guy she worked with. He called her cell phone about 3 months before this happened and i told her to tell him to never call again. She wouldn't do it because she claimed that she didn't want ackwardness at the workplace and i understood because she hates confrontations. However, i told her i didn't like the fact of her talking to this guy. Anyway, about a week ago she told me she was at work and she was really at the guy's house. She was there for about 3 hours and said she went there because she had doubts about being with me for a long period of time. This is her first serious relationship. I had a gut feeling and went to her work only to not find her there. She didn't come clean with me about what happened so i asked the guy and it turned out she lied to me because she said she didn't do anything. She ended up making out with him. Since then i broke up with her because of it. I told her we can remain friends until she gains my trust back. She pleaded and pleaded with me for the week that she will change and tell me the truth from now on about where she is and what she is doing and work really hard and never cheat again. She has done a good job of it so far but has complained a lot about the checking up and being harsh (which i've kind've been). I took her back and told her that in a month if nothing changes we are done. She told me she loved me a couple times but it turns out when she was being totally honest with me when we had a heart to heart convo the other night she didn't mean it. She told me each time she loved me turned out not to be true. So i asked her if she is in love with me and she told me that she is now because ever since she lost me she realizes what she missed and the mistake she made. I felt like even though it was a week could this happen so quickly for her to feel like this, or does she just hate being alone? Anyway, we are together now and also it turns out she lied to me our whole relationship. She told me she was sexually active before this relationship with two people and was straight forward with me that i was her first because she didn't want to feel like an idiot because i was experienced sexually. I told her that was silly and i would've accepted her for how she was regardless. I have done a lot of things right, i have treated her good, drove her places, paid almost all of the time.. maybe my flaw has been pressuring and forcing a lil? idk...she has done her fair share of good things too, but i always had to push it a little for her to treat me kind of well, what i don't understand is why she feels the need to lie to me and cheat and i would like some advice why you might think she would do that and if i should forgive her or move on????...thanks.also...i've asked her why she went over there and she made plans with him a day in advance and is sayin it happened too quickly...i told her like...how come u didnt pull away from kissing him and she doesn't have an answer...ive asked why she did it...she she didnt tell me etc. and she doesn't have any answers....i feel as though she likes him and just isn't telling me....but she said he is hideous and disgusting but it's like...uhhh why would u kiss sum1 if they r hideous and disgusting? idk....im so confused because i love her so much...but she isnt giving me straight answers....i feel like it's all just bull that she liked him but then idk why she would stay with me if she liked sum1 else if she actually liked him....or if it's sum weird girl phase because im her first serious relationship and her first sexual partner....idk help me though i know it's a lot but i hope people were patient enough with me!

dump her if she lies to you, she can't be trusted, and she's obviously unworthy of your trust