Had to check we weren't in AIBU because the OP doesn't seem to be being taken seriously here by a lot of posters. If it was a woman posting, she'd get far more kindly and careful responses imo. I'm sorry you've been subjected to some vile posts here OP (the lesbian one stands out
) as well as some posters largely talking over your head and treating the whole thing (which is 'ripping you apart') like a joke. Shame on you MNers.
OP, one thing: how do you get time to go to the gym? What is she doing while you're at the gym?
ok, two: what do you mean 'the life you give her'? You have a deal: she keeps the home, you go out to work. It could be the other way around, she could go out to work and you'd get the thrilling home job. Working at home can be soul-destroying - you have to be endlessly creative to make cleaning up for the 5,823rd time seem a worthwhile thing to do. You, meanwhile, get to see people, go here, go there - you're a free agent during working hours, up to a point (and, it seems, after working hours re gym). If she's at home with a 3yo she probably isn't a free agent for hours/days/weeks/months on end. Do you get up in the night for the kids?
If you're 'giving her' a 'good' life (what is she 'giving' you? She gives you a lovely home, domestic set-up and lovely kids) and you've time to regularly go to the gym, you could be acting like a single bloke - life not changed too much since the kids came along (whereas hers has probably changed beyond recognition). If so, that would piss her off BIG time and all ardour would vanish. Have you ever had the kids for the w/e while she goes off to do something lovely for herself? 1. She'd get a break and 2. you'd see how gruelling childcare is in a big chunk. Which is her daily life and has been for years.
I'm not saying you don't work hard and I'm also not saying that going to the gym is a crime (though I can't honestly see how you have the time to go regularly if you have a young family). I also don't know what her day looks like - she could be getting help and mummy-free time etc.
I'm sorry this is so painful for you.