Want to loose weight

Hi im a Crohns suffer an last year I had to be admitted to hospital for 3 emergency major opperations very complexd opperations now my tummy muscles are very weak but I want to lose weight I was only 9st/6 before i went in to hospital I was in there for 5months not very active at all down to the surgery when I was sent home I weighed 11st I was told to walk as much as I can to loose the weight which I've done but I'm now 12st I want to do more excersice but not sure what's safe as I also had an hernia repair in tummy as well it's really getting me down coz I can't for the life of me seem to loose anything I'm 59 years old never been this size before in my life an it's affecting things like getting out of breath no energy what can I do ?