Once a cheater always a cheater?

Late last year, my boyfriend cheated on me multiple times. He even cheated on me with someone that was close to me. I found out about his cheating through his phone one night when he fell asleep with it unlocked in his hand.

He begged for me to stay. Said he would do what it takes to fix it. I considered staying mostly because our son is not even a year old. I know staying for the kids is not the best decision but I felt I had to. My condition was we have an open phone relationship and we inform eachother of our whereabouts. I never felt like I can forgive him however, I dead the issue because I really wanted things to be better between us if I was choosing to stay.

Things was improving, however this year I've been feeling very suspicious of him. The same gut feeling I've had that led me to go through his phone the first time. The condition that we had to have an open phone relationship has gone out the window. He hides his phone 24/7. He even goes with it in the bathroom and it's always in his pocket. If I happen to sit next to it while it is on charge, he would take it immediately and walk around with it. He is a person that is glued to his phone and always has been. I addressed the issue to him and he said he still has rights to some privacy. I do not agree. But he hasn't gone through mine so I don't know how to handle this.

Last night he went out to meet with a guy friend of his, at least that's what he told me. I never had any proof if it was the truth as we sometimes send pictures to eachother when out with other people but last night he did not. He came home around 9pm. And this morning he woke up early and was texting on whatsapp. It was an intense conversation as he was fixated on his phone for a few hours. I could see him smiling here and there. I was so tempted to ask him who he's talking to but I know he was just going to make it "my" issue and I honestly do not need an argument.

I don't have any proof just suspicions. Could I just be paranoid because he cheated before or there is something there? It won't matter to confront him because he's just going to lie to me. I'm even at a point where I want to hire a hacker to get through his phone. I never had the password. He would ask me often if there's someone I'm talking to so I don't know why he would care if he's talking to someone else too. He wants me to tell him wherever I go but I don't see him doing the same. Things also feel dead between us. We have sex once a month, maybe twice. Some days things are better than other days. I had already bought him a Valentine's day gift but I'm sure I'm not getting one. If he's still cheating I'm leaving this time and I've already made up my mind about that.

Anyone know what I can do to find concrete evidence? Is it fair to break up with someone just over suspicions? He gaurds his phone extra now so the chance of getting it unlocked is slim. What is the right thing to do? I want to be wrong so badly. In need of some wise advice please.