Newbie needs advice

Hello, I have a big problem. I should start with some backround. My high school sweethart and I had a on off relationship in our teens. We both used to see other people a such, back then it wasnt that serious. We always argued about infidelity and slept with people out of revenge or just because and I never got too close out of fear of being too attached to a woman who liked to have more than one man. After e split she moved in with another guy. One day when he was out of town she came to see me and it happened to be the day we conceived our first child. I was 20 at the time. She was 18. In the yaers following we went on with our lives having minimal contact unless necessary for seeing my son. She was in a serious relationship and I got married. We somehow ended up together again after 7 years. I devorced my wife to be with her(no kids from the mairrage) as my ex was horrible and tried to keep me from being in my sons life out of jealousy or something. I figured I would be happier with my son and his mother. We had our second son on the way before I knew it. I will never regret having another child with her because they are my world and all that matters is that they are happy and raised right. Almost immediatley after he was born she started coming home very late like 3 to 5 am. saying she was with her friends or sister or that she was drunk and slept on a friends couch. I was enraged but we had a 4 month old baby and an 8 yr ols to raise so I held my course. Over time it became more frequent. She wouldnt take my calls while out saying she forgot the phone in the car or some other excuse. She sometimes just decided to go out and not tell me or take calls. I am home with my young kids every night and dont much enjoy the bar scene so I eventually became used to the behavior telling myself its normal for her to blow off steam with friends once a week. I never approved of it but had to live with it and without proof i had nothing to stand on. As you all know raising kids can put a damper on the sex life. She was sleeping on the couch for a year after our second child was born because she had some back problems and was more comfortable that way. After she decided to start sleeping in our bed again neither of us could sleep so I started to sleep on the couch, at least until late when I could move to the bed without waking her. Needless to say it affected our sex life greatly, and intimacy is at almost zero. On top of the seperate sleeping issue I have the late night outings on my mind all of the time. One night she came home late and horny and we had sex and slept great. In the morning she went to the bathroom and I looked at the phone. She had texted her ex of 7 yrs repeatedly telling, begging him to meet her at the bar. He declined. Another text to another man at 1 am (closing time) said "duty calls here" hes a state cop. Im no dummy and I know what that meant. I confronted her and she apoligized for the inappropriate texts and claimed to just want to talk to him and that it was a mistake. I grudgingly took the bait.

That was 6 months ago. For over 4 yrs I have been seeing ramdon signs that to me are red flags
late nights out without me
not answering my calls
lying about location
lack of intrest in sex with me(once a month usually)
lack of intrest in our relationship
telling me to leave when she is angry
told me she doesnt feel love for me anymore
actualy served me with custody papers but changed her mind when she realised I would have the kids every week night.
constantly on phone and facebook
never leaves the phone even while sleeping or in the shower
accuses me of cheating when I confront her
makes mr feel guilty about questioning her

for the record shes no angel, she cheated on 3 of her ex BF with me over the course of 10 yrs and she was working as a stripper for most of the time that we were living seperatly. I love her and worry about the kids mostly, but I cant live with myself knowing Im just there to take care of the kids (she works till 930 pm)and pay her bills. I want proof, and have considered the smart phone spy stuff. Do I really want to know? should i try to get primary custody and leave her? I would rather have a happy family but after reading this forum most of my suspicions have been confirmed. My gut says im an idiot.