Can u be forced to take FMLA leave by ur employers?

Knew was needing surgery 4 almost 2yrs but kept working bc couldnt afford to take off 3mo.My boss knew about light duty from dr & approved of it for almost yr till corp office got mad it wasnt in writting. I was told could not come back to work without excuse & had dr fax them her personal letter. Next day was told could not return to work until had surgery. I was told I was gonna be on FMLA leave & only way to stay. I had no notice of income lost, Im single mother just wanting to work & be payed 4 it only! Also, got no unemployment either, no help at all. Please tell me they cant do this to people, how can they decide about my healthcare? Im even on management crew, imagine how theyd threw me out if I wasnt!