medical leave and harrassment

I have been employed at my work for 13 years.I have been a very good worker and very well liked by fellow employees and customers. In the past year, I have had a lot of medical problems and am at present I am on medical leave for sciatica. Management does not feel I have a valid excuse to be off work and have called me a hypochondriac and asked me how I can afford all the doctor visits. I have another small bookkeeping job which I do mostly at home and they have been harrassing me there. I have always turned in Drs. excuses when I'm sick and I have medical reports to prove I have medical problems. I'm 54 and single and I need my job to pay my ins. and house payment. Someone has been talking to my fellow employees and they turn their back on me when I'm in the store and don't speek. I have done nothing to cause this and I'm not sure I can handle going back to work there when I am released by my doctor. Because this is a small town and my medical problems I'm not sure I can get another job and I don't want to lose my home. Please advise me.