I feel like it’s not really sustainable

It's absolutely sustainable. Lifting weights is not that hard

I store a lot of fat in my stomach in general so when I’m bulking my figure goes to shit

Bulk slower. You shouldn't get super fluffy the moment you start bulking.

look better overall when I’m a lower weight

Everybody (except anorexics) look better at a lower weight. Doesn't mean bulking aint worth it

my gains shrink a LOT

99% chance it's all in your head. Muscle doesn't just atrophy that quickly lol (I haven't lifted seriously in months and I hardly notice a difference in muscle mass. Been cutting too btw).

I’m thinking I should just accept how I am

You should definitely accept yourself, but that doesn't mean you just give up on bettering yourself.