Exercise gives me anxiety attacks but gaining weight also gives me anxiety. how do i deal with this?

Anxiety won't help: You make the choice - exercise or gain weight. You can't pick one just because it spares you anxiety. So, pick on another, better basis. But even after you've decided which to do, you need to learn how to manage anxiety. Cbt therapy (with or without meds) is a good way to develop skills. It can be like a gym coach in helping you work through hard spots, to get past them and move more freely. Best!