I Need To Vent And I Need Your Advice. It’s Long. Please Don’t Be Rude.?

I have an icky gut feeling that my fiance is cheating on me. I suspect he has paid for and been with hookers since we’ve been seeing each other but I really think he has someone else in his life specifically.
He is always telling me I am his only one and when I hear it I believe it but his actions don’t match up. For instance everytime I try to get in touch with him for something REALLY important, he is incognito. Wont answer the phone wont call back. Will pretend like he didn’t get my text when I bring it up.
He used to call during lunch, now he calls after lunch when he’s about to go back to work. He got offered a new job in town. He made up some baloney excuse to go back to the job he HATES that is 2 hours away. Yet he says he wants to be closer. I can’t help but think he is spending time with another woman.
It could just be insecurity but I can’t help it. I’ve caught him flirting with women online before when he SWORE up and down that he would always respect me. We both had a long conversation before we became a couple and told each other that we would be open and honest. I promised him that in relationships I don’t flirt with other men or even initiate conversations with other men bc I don’t want to put myself in the position to cheat– bc u can’t fall in love with someone u don’t know.
He said he felt the same as me and when he’s with someone he beats down feelings of attraction bc he’s not a cheating man. Now I know men check women out but he was talking about not pursuing them. I even tell him when guys ask me out because I want to be held accountable and stop temptation! He said he would do the same but I wonder (we believe that keeping it a secret invites secret communication between that third party and bc people get weak we dont want to even have that as an option). Of course, I took him at his word and felt that we had a strong connection. After a while, we eventually became an exclusive couple.
YET I was using the computer one day and typing in a site when TAGGED came up in the results and I clicked on it. He was still logged in and his profile said SINGLE, looking for Dating. Feeling betrayed, I read his msgs and saw him emailing women telling them how beautiful they were and he wanted to take them out to dinner.
I didn’t see any women responding back but he was fishing! But I confronted him and he said tagged is a flirt site and everyone does it. Nobody hooks up and he would never go out with the girls. He said it was an ego thing. I asked people on YA and they said to dump his ***. I should have listened but I bought his line. Plus recently he said that he hasn’t been on there since I confronted him but his profile says 2 months ago was his last visit AND it still says single and I don’t remember him having ‘serious relationship’ under the seeking part.
Now almost a year later, I am still insecure about it. I still feel betrayed, why lie about beating down attraction for other women if you know you are going to be flirting with them and pursuing them?
I share my concerns with him and he assures me that he is being faithful, but don’t all cheaters? I don’t want to be accusing him of cheating but I can’t help it when something seems fishy. I was getting suspicious right before I found his cyber profile.
I called him several times one morning during a semi-emergency and he didn’t answer. He called back hours later and said he didn’t hear the phone it was in his pocket. But when we’re together, his ringer is loud as all hell and it vibrates! So my mind tells me that he was on the phone with someone else.
He’s always taking like $40-$70 out at the ATM from our bank account every week and still using the debit card for other stuff. So could he be buying hookers or giving some woman money?
Once I went into my internet history to revisit a site and I saw he had been online looking at porn and looking for local escorts! I dont think he actually called/bought any but how can I know for sure? I was working the night shift during that time.
When I saw the hooker ads and porn and found out about his cyber flirting, my love lessened for him but I still love him. All of these paranoid feelings are making me fall out of love with him and I know it’s going to push him away if I keep it up.
Still I can’t be rational about it. In my head, he IS cheating (and thats not fair to him if he’s not) but I can’t shake the feeling that I’m right. My friend said I need to put some spyware on his phone to just get piece of mind. But I dont feel comfortable doing that and im sure its illegal.
If he is only looking at porn and browsing hooker ads out of curiousity, then I can deal but if he is talking with, flirting with, emotionally/physically cheating then I have to walk away. But I won’t do that on a gut feeling. So what else can I do to