I think she cheated!! Should i believe her?

we have been living together for a year, lately things hadn't been that great between us arguing etc. Well anyway recently she confronted me and told me she wanted to break up, now a week prior to that she had said if i didn't start becoming more motivated about going to school she would lose interest in me. Anyway 2 days after she broke up with me i found this text msg Tj: so are you gonna be with sheldon now? Jess: i don't know im taking it slow. Now im still living with her until the end of the month so it's rough. I confronted her about it and she said that she didn't break up with me over him and she had just recently been talking to him ( she knew him from other friends from along time ago) and it didn't matter because we were broken up. I was like yeah it does, if you broke up with me, for him technically that's cheating. She said they never did anything together and she didn't cheat on me. Now she said she would stop seeing him because i reemed her *** about(maybe she is waiting for me to leave?) it and it was too much drama for her. Anyway the last 4 days our we have started hitting it off and it's like we are a couple again... but i think I'm still going to move out the end of the month. She would always give me a hard time thinking i wanted to cheat on her and she had deep insecurity issues, constantly badgering me if she thought i was looking or talking to a girl. Should i believe her in any of this? Our take her back if that happens ? should i still be friends with her... which she wants me to be? we Love each other a lot, that part is true.