Firstly I've name changed so as not to out but I'm a regular.
I really don't know what to do about this situation which has been on/off for the past year. Basically dp goes to the gym regularly (all fine) but he seems to have developed a relationship with a much younger gym go-er, think 35 (him) and 25 (her). Anyway she works there and isn't a fitness instructor but I found out that they were doing fitness classes together, i.e her "running" a class unofficially in the gym for him and another girl. This didn't sit well with me as this is something we used to do together and haven't been able to due to having small children.
At the same time he was pm her and the other girl, just chatty messages but I asked him to stop as I wasn't comfortable with the situation. He also stopped the extra fitness classes. Well i thought he had until I read one of his messages today and noticed they had tried to reschedule one for last week, this has made my blood boil. He's clearly been contacting her and deleting her msgs/still doing some sort of fitness related activities with her and lying about it.
To put this in context I find this quite intimate as this is something we used to do together but can't at the moment. I am also unhappy that he is keeping it from me. Our marriage is in a fragile state I would say, very little intimacy in any form since recent baby came along. I feel like a trapped "house wife" and I feel pretty shit in myself (1.5 stone overweight still) etc etc.
I don't know what to do, part of me wants to tell him to do one but then the other part of me thinks I am over reacting... What would you do? I can ask him but I'm scared I look a paranoid freak :(