How can i lose weight when im on weight gaining medication and cant exercise?!

I am on medication which I must take for my health, and it is weight gaining. It basically makes my metabolism as slow as if it were in starvation mode (all of the time) and especially after i take it in the evening.

I am on Risperidone. 1.5mg a night.

It increases my appetite and slows down my metabolism, however due to my strong will I can pretty much go the whole day and night following a very low calorie diet, which by the way seems to be the only thing that works for weight loss as doing a normal calorie diet does NOTHING and i stay the same or even GAIN weight. yeah thats right!

Did i mention that if i do intense exercise for over 15 minutes a day, I become really sick with a bad cold/cough/flu that lasts for about 2 weeks and if i return to the exercise i get sick again?

So I know its wrong to starve myself, because Ill have fainting spells and become weak
and I cant over exercise or i get sick

So how am I supposed to lose those last 8 kilos to reveal the flat stomach and lean body I used to have BEFORE this medication.

Also: I am already on the lowest dose of medication and its the only drug that known to work so i cannot and will not change it.