at my age! Fat stores estrogen, so when we lose fat, the estrogen is released.  This can cause you to have changes in your cycles.  Because you have started having periods again, you are probably ovulating and should take precautions (birth control) to be safe. I'm 37 had not had period since my IUD was placed in January..had my first one the day of surgery in September..my OB said it was from weight loss and my IUD shifted due to it...as long as I keep losing I'll deal with the period!! I am 48 & I will be 49 in Dec. oh my almost 50 lol but what everybody is telling you it is normall either it is due to the surgery or ask your ob/gyn if you might be perimenopausal as I know I am so I may not have one for 2 months then here it comes again , so it's off & on . I was also worried so I made sure & asked my primary doctor , then I also asked the surgeon if it was normall they both said yes also I have a I U D but I don't want any more children at all .