What to do if I suspect my wife is having an affair?

Having big trouble in marriage. My wife is constantly complaining that I dont make enough money and criticizing me for being controlling. I think she is seeing a guy she knows from work. She comes in very late from work 3-4 times a week. I mean like 3 hours late and says she was working late or going shopping. Its getting to where we hardly evemn talk or see each other. friend of mine followed her from work and saw her meet up with this guy at a bar. She denies it and says she was having drinks with friends at work. She says that she is unhappy, that our life is boring and she has lost interest in me because I dont give her freedom. Says she is very miserable in her job and needs space to think about what to do about her career. She has brought up seberal times that maybe we should separate so she can have some space. I dont know what to do.

Given all the things that you said in the above there's really nothing else you can do but separate. No matter what you say or do it sounds like she's going to do what she wants anyway. I'm sorry that things aren't working out for you and I hope that you don't have children because they're the ones whom are worse effected by a troubled marriage

You didn't mention your ages but I'm betting 30s and most likely late 30s. At any rate, it sounds like she has hit that "Last Chance to Trade Up" mode. It's common for many women, even if they secretly decide they are safer where they are. Things are much worse during that period if she earns as much or more as her husband. It sounds like she is pretty far gone but that might change in a hurry if her potential trade backs off. Maybe you could threaten him with an alienation of affection lawsuit if she leaves you. If it was easy to follow her, it might be easy for you or a friend to accidentally see them and introduce yourselves. Nothing ends a meeting of secret lovers like being joined by family and/or friends.