How do I tell my boyfriend I dont want to work out?

My boyfriend is all about weight gain, getting cut, and being super fit. He has been asking my since we got together to join him. And I have tried. I've tried videos going to the gym joining my friends cross fit group anything I can think of. But I hate working out. I'm an artist, I was never athletic at all. I don't know what to do. He keeps pushing me and telling me to work out. Its making me feel terrible because I feel like he doesn't like my body and my lifestyle choices.
How do I tell my boyfriend I dont want to work out?
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