Very low energy and weight gain

Hello,

I still have very low stamina (stay in bad 60% of day time) but I gained a lot of weight. I don't understand why.

I started to gain weight when took Zyprexa (olanzapine) for sleep but I continued to become fatter and fatter (in the abdomen area especially)

Why my body doesn't use this energy and stock it?

Any idea?
I am slightly hypothyroid but it is a very small deviation and is old.

Thanks
Anca Tweet