S.W.
K.-
I started my period with both my kids were 13 months and I nursed my daughter until she was 2 1/2 yrs. I think 13 months is the average although some women (like you) don't start their periods until completely after weaning. I would definitely say the weight loss could have something to do with not starting your period yet either. Although you do not consider yourself skinny, that is almost 20% of your body weight that you lost. Hormone balances change drastically. I would just say use some form of birth control if you aren't already and just relax, your body is probably just trying to get back in the rhythm.
Brekka