Now before anything, I don't have any proof of her cheating, that being said, here's what led me to believe that she might be or maybe has been. So me and my girlfriend have been together for 5 years, we had a child when she was 17 , we finished highschool with honors and we took jobs of oppisite shifts (like me working 1st shift while she worked 2nd shift) at the same company. we did that cause we obviously couldn't afford a babysitter at the time. things were rough and we both didn't really get to see each other until the weekends.. we were having sex maybe once a week or even longer then that, and as time went on we started just being mean to each other out of stress, I don't know why but she started being on her phone a lot so I would play around with her and be like "hey you better not be cheating on me by texting ur lover" or something like that (can't really remember) and she would brush it off even tho her and her phone got really attached. I recall I tried going through her phone one day, and she got seriously pissed at me for doing so and  scolded me about privacy and what not. I obliged and decided not to mess with it, although it still hurt me that I couldn't even see into my own girlfriends phone, like she goes through my phone all the time , not like I have anything to hide.. so one night, I decided to ask her to let me see her phone and she refused, so I asked it again and she still said no. eventually we argued and and she finally got fed up and decided to leave me over me wanting to see her phone.. I couldn't believe it, all that we been through and she threw it away.. I was crushed.. I couldn't do my work right at the job, I felt lifeless and I Persued her into taking me back and after a month (and merging of the 1st shift and second shift) she finally took me back, although it was only when I finally thought I should give up that she decided she wanted to be with me.. anyway forward 2 years more into it, we were happy, better then ever, I was happy to see my daughter again and be in her life. I eventually left that job where we could see each other all the time to get a higher paying job and things were great, just that we barely had sex at all.. I would be lucky to get some once a month.. so one day I saw her phone on the bed and I recalled this incident and we never did get closure on the whole phone incident so I decided to get on her phone while she showered and went on to her face book page and I noticed she was messegeing a guy all flirty like (something I never got) and they were saying stuff like they miss each other and how they cared for each other... I was crushed... my gf always told me about her work and how she holds up but she never mentioned that guy before.. so she comes out the shower and I tell her about our past incident about the phone thing and how it's stupid and all that we fought over a phone and she laughed and agreed as well and I asked her if I could look through her phone then if she believed that. so she says yeah u can but she wanted to do some "stuff" on there first, which I allowed cause I didn't wanna seem suspicious and after maybe 30 mins, she decides to let me go through it for the first time. so I got it and went straight to face book and bam, the messeges were deleted.. this obviously hurt me again, I mean come on, I even gave her a chance to come clean.. so I told her that there's a messege missing and she denies it and saying she didn't delete anything, she even swore it on our daughter.. like wth.. since my story is long enough, we argued about it and she said it was a friend who use to work where she works (not anymore) and that apparently he had a thing for her but she said she accidently flirted back... like really? and so I told her is that the only guy, and I asked her to be honest with me and she confesses that she flirted with another guy back when she was in 2nd shift cause he was cute and that she was lonley, which i can understand that but still... I told her that all those times I was offered sex at work, I always turned it down out of respect for her and never once thought about cheating on her. so she tells me that she only flirted with these men and that nothing physical has happend.. I seriously don't know what to believe since she tried hiding it and lieing about it and I'm just so crushed by it that I just want advice.. is that cheating? do u think she has cheated?