Study up on diabetes, it can cause circulation problems in the legs and feet. Until you said that, I was getting ready to tell you that poor circulation from too much weight can make your legs feel numb and stiff like that, but so can damage to the spine. I'm both overweight and have a serious back injury, my legs are all goofed up, stiff, limping, some neuropathy, and just the other day both my feet got numb. But if you've got diabetes, you are in luck, if such a thing can be characterized as lucky, because it can be controlled by managing insulin levels in the body. Do as your diabetic doctor tells you, and you'll be okay. As for exercising again to lose some weight, you can do all sorts of exercise without putting too much pressure on your legs and spine, like swimming is an excellent sport for someone whose legs can't take the banging around that running does. Really, anything that will cause you to break a sweat will help you lose weight. Also, if you can manage to get a good exercise programme going again, and you do lose weight, SOMEtimes that will take care of diabetes, to where it won't be a health issue for you anymore.
Ironically days after posting this I was diagnosed with new onset diabetes. Suddenly I have a new fear of what is causing my nerve issues in my legs. this stuff makes me scared.