Hi - new here - plus sized lady hoping to lose weight

hi all, I'm a plus sized lady weighing 17st. I am a disabled 28 year old lady whose on both slow and fast action morphine. I would like to lose 7 stone. However I'm unable to exercise other than around the block walk, and I have a sweet tooth. I am on orlistat tablets so hoping with this, my will power and orlistat I may be able to get to the weight I was before I had my daughter and before I become poorly which was 8st and a size 6-8. Really need as much motivation as possible please.

Thanks xx