My sister didn't get any periods until she stopped breastfeeding (when her LO was a year old)!
I think it can be normal because of the hormones breastfeeding releases. Some people don't get a period until they stop breastfeeding, others get them straight after birth, and some get them somewhere in between - perhaps your symptoms are a sign that your periods will start again soon...
If you're at all worried, though maybe contact your doctor?
Hope things settle down for you soon, hun - take care
