Ok I will be 40 in a few weeks and have had 4 kids. since early 2005?

I started stacking on weight and at my heaviest which was 3 weeks ago I weight a grouse 70 kilos bleh. which would be about 150 pounds YUCK and I am 5ft6. I have been watching what I eat and running, as I used to be a very competitive runner many years ago, and since I have been running and eating better I have lost 10 pounds in 3 weeks.now I weight about 65-66kilos. what do you consider a perfect weight for my age and hight and the fact I have given birth to 4 kids? by the way I am heading into menopause. According to a doctor he said do not go down any lower then 60 kilos. do you agree? I have droped a dress size in 3 weeks. yes quick, as most cannot do that my age. so what I want to know is what do you consider a perfect weight for me? am I at that now do you think? I feel so much better and my blood presure is now 100 on 70 and my resting heart rate the other day was at its lowest of 41-42 beats per minute. as I said I used to be a top athlete. thanks