How much weight do I have to lose to regulate my period again?

Over the past 4 years I have steadily been gaining weight. I ballooned up to 198 at my highest! I am only 5'4. I got off the pill in July of last year (my husband and I are trying to conceive) and only had three periods on my own over a 7 month time frame. The doctor suggested that it was probably my weight; which made sense considering I used to be much thinner (about 140-145 pounds) and had never had a problem with periods prior to getting on the pill. Hearing that really kicked me into gear and I completely overhauled my life. I have lost 20 pounds already and am eating well balanced, healthy, nutritional foods as well as exercising at least an hour a day. It has only been a month and a half since I started dieting and I still don't have any sign of a period. My last period was March 9, 2010 and that was after I was prescribed Provera. I am trying to be optimistic but it is really hard when you are only 23 and can't menstruate on your own! Anyone have any similar stories?