YO! Y'ALL!

I've read here and elsewhere, including Atkins about yo-yo dieting making it harder to lose. I'd like to know what constitutes yo-yo dieting? How does it affect rate of loss? And I'd like to know if, by definition, I'm a yo-yo? (My husband might agree.) In a nuthshell, here's my diet history: (and what would you make of this pattern?):

Age: 20-30's: 122-126 lbs

Age: 30: 146 lbs - followed two diets, Jane Fonda the carb queen!, and Nutri-System (remember? Foul!)
Went from 146 to 135.

Age: 34: 137 lbs. Made up my own starvation diet to get down to 122. By the end of it, I was eating cans of tuna.

Over the next 10 years fed up with diets, ate whatever I wanted, but oddly, read tons of diet and exercise books! ( Vicarious living indeed! During these years, I also became hypothyroid which probably contributed to some of this weight gain. Now treated.

Age: 34-44 slowly crept up to a peak of 169.
During that time plateaued at 157, then 162, peaking at 169, which prompted:

Age: 44: 169lbs. Atkins, went from 169-145. Went back to old way of eating. Regained all but 7 lbs.

Age: 45: 162 Atkins (Started currently, Jan. 2000) with goal weight of 125. Finally realised I can't just eat whatever I put my hands on.

Does this make me a yo-yo dieter? Will it likely affect my diet? Have I ruined my metabolism. Is there some diet guru who knows these things? Thanks for any help,

Ruby