Honey, your husband is having an affair. What will it take for you to acknowledge this fact?
The first time something happened to pique your curiosity, his hot redheaded co-worker's husband threatened to beat him up at a bar for cheating with his wife. Not to mention this happened in front of a large group of other co-workers.
That should have been a red flag. You believed his story that the husband was a nutcase (which is possible) that the girl was a nutcase (which is also possible) and that she made the story up to make her husband jealous. As strange as that story was, you believed it. I actually admired your strength and willingness to believe your husband and loyalty to him.
The next incident involved finding not only her name and number on his phone, but calls to and from her. Your husband claimed that since he is out on the road all day, and she is the office manager, he needs to be in contact with her and it is sometimes easier to use cell phones than the office line. OK. I might be able to buy this in isolation.
Now, a third party - a guy - we'll call him John - that you have met and socialized with and who seems like a nice guy, has contacted redhead's husband, who is away at basic training, to tell him that your husband is having an affair wtih his wife. Now why would John do this? Why? No explanation makes sense except that he is telling the truth - your husband and the redheaded hottie are having an affair.
Your husband called you at work to tell you what had gone down. He was afraid that John would contact you. He claims that John made a pass at Redhead and she rejected him so now he is bitter and looking for revenge. He claims that John is crazy. He claims that Redhead might have told John this.
Sorry hun, but where there's smoke there's fire. This has gone on long enough - 4 years to be exact. You've looked the other way, made excuses, and bought what he has told you. I think one incident can be explained away, but 3?
Now, I'll admit, I'm not your husband's biggest fan. He can be rude, he doesn't treat you the way I think a husband should treat his wife, and he complains if you so much as run to the store and leave him alone with his children for an hour. You wait on him hand and foot, and yet he complains constantly.
I'm sorry, but I've held it in long enough. Look at the big picture, and see what is right in front of you. You CAN walk away from him. You deserve better! You have your wonderful family and friends who will support you and get you through this. But please, take the blinders off and see what everyone else has seen for a while now.