He's on Match.com

[Dom R]

I tried the gym in the past. Hate it. I don't get endorphins, I get sleepy and mad.

Maybe he's right; I can't be what he wants.

you're kidding me... you're giving up that easily?

Perspective #1:
If you knew that your children needed money for [living, whatever], and the only way you could feel confident of giving that to them in a stable manner, was spending 8 hours a day in a job that you didnt particularly like: wouldnt you still go spend those 8 hours a day, 5 days a week doing it?

If so, then why wouldnt you spend 2 hours a week, taking care of something that you know your marriage needs, even if you dont particularly like it?

Perspective #2:
Why did you get "sleepy and mad" at the gym?
What did you try, and for how long did you try it?
"let's discuss".

Perspective #3:
"go to the gym" is one way to get a toned body. It is by no means the only way. There are many many others.
The odds are quite high that you would find at least one of them fun

[If you want suggestions on alternative activities, then you should post your height, weight, and approximate strength/stamina. ]