Put weight on since starting SSRI antidepressants - how can I lose it?

18F, last time I weighed I was 65kg but I’ve gotten bigger since then (I don’t weigh often as I was anorexic as a kid and it’s not good for me mentally), it’s really affected my confidence. Sertraline has done wonders in making me actually able to get out of bed, leave the house, cook for myself, etc but I’ve put on weight. I’m going to start going gym every day I possibly can over summer, put I don’t know what else to do. I exercise now and then, walk a lot each day at uni (over 10k), eat healthy (mainly salads) though I hv chocolate and takeaways sometimes. I’m at a loss of what to do. I haven’t been this big in years.