Debbie, go get a complete physical with bloodwork, etc. and make sure it isn't thyroid or some other such thing in the "way" or meds (you still on any meds) and that you are going about the whole thing from a complete-as-possible point.
I have a similar problem to yours. I'm 57, 5'6" and when I was 25-26 weighed 127 no matter what I ate. But I only gained steadily, didn't do anything drastic like not eat. When I was 38 I lost 20 pounds on NutriSystem for only $2,000 and only gained back 80 pounds :-) I tend to not do "diets" anymore for some reason. Four years ago I had medical problems for 5 months and lost about 25-30 pounds as a result but have gained back most of that weight. Gaining and losing weight and getting older, ill, etc. does a number on one's body. We can't do anything drastic at this point or it will only make it worse.
I'm concentrating on the fact that I gained 125 pounds in 25 years so I may have to lose 5 pounds a year for the next 25 :-) It's not going to come off like it use to. Now, more than ever I need to get a good routine going of eating "correctly" and some good activities (I don't do "exercise" anymore after two disasterous attempts).
But I would go to the doctor and get a really thorough physical with everything checked from bowels to nuts :-) blood, heart, lungs, blood pressure, chloresterol, diabetes, thyroid and other endocrinological things, etc. I would study 2-3 good eating plans from medical types or established groups -- the DASH diet, for example:
http://www.dashforhealth.com/ or weight watchers and see what I could use and make my own. I'd keep a diary of sorts (I like Chef Kathleen's
Cooking Thin Daybook http://www.kathleendaelemans.com/ she use to be 80 pounds overweight and a chef! Read her bio, very interesting) and I'd figure out what my difficulties are (for me, too much meat and beer :-).
The weight took awhile to put on, it should take at least that long to come off so it stays off.