How do you force yourself to exercise?

For me exercise is pure misery so enjoyment is not a factor. I usually get "exercise" from cardio or walking because I'm a usps mail carrier and that maintained me for the most part. Now though it's not working anymore because my body is used to it and now I'm gaining weight.

Problem is I can't stand working out and i just have no energy because of work.

Mind you i have done the gym life before because i used to be fat and I worked through the misery but that was before i worked this job and I was younger. I hated every second of it but i did it because i wanted to try not being fat.

Technically i don't care about becoming fat again for the most part but I'd rather not go back in full fat mode again because that would make work even harder.

I don't know how to force myself to do anything because i honestly don't care enough about anything due to mental issues.

I'm 30. I own a few free weights, have a weight bench that was given to me as a gift that i rarely use, and a stepping machine.

What can i do?

Edit: I hate sports.