I'm just going to post and run for now, as I can feel an urge to write at length and get involved - and I'm shattered!
I did it. To try and summarise a fairly nasty layer-cake of underlying causes: I was raised to believe that all men cheat given the chance, and all women would try to 'lead men astray'. Despite knowing these were fucked-up values, and having rejected them intellectually, the beliefs were still immensely strong. Consequentially, I chose partners who were liable to cheat and lie - it was what I expected and, basically, I didn't believe there was any other sort.
Said underlying values naturally led to my being suspicious, even when a more secure wife wouldn't be. Although I had/have a sophisticated arsenal of subtle policing techniques, the men I chose were alert to my suspicions because they did, in fact, have something to hide. Have I lost you yet?!
There were lots of rows, of course. My beliefs said "He will cheat if he gets the chance, and it's up to me to try and stop him." Daft, but that's the way my parents operated and, tbh, stories in the media tend to support their view. A woman's job is to be so fabulous a wife that her man can't find any better, and so efficient a guard that he doesn't get much chance to look 
Obviously, normal life provides endless opportunities to cheat. I couldn't police them all without locking him in the cellar. Despite knowing this and being logically calm about it, I was in constant torment underneath. It didn't help that my partners were, in fact, lying. Thanks to all the suppression, fear and self-control over my urge to police the relationship, I didn't have any proper functional means to deal with fairly obvious dishonesty. I just got more and more fearful, veering wildly between denial and accusation.
The second Mr Garlic was a horrendous game-player. I now believe he enjoyed seeing how far he could push my denial and how guilty he could make me feel for doubting him. The bastard. It worked, and was utterly horrible. I felt completely trapped. What was really trapping me was the inherited belief system - he played on it, abusively - but I didn't see that until some time after we divorced.