You may not get your period while your are breastfeeding because prolactin levels are still high. However, you may be ovulating though. So, be careful when you start having sex again, use protection if you don't want to get pregnant again so soon.
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EllenG.
Steadyhealth.com
Sorry I can't tell you why you are getting those sharp pains, but I would see a doctor about it. It could be anything from gas to your appendix.
Your period will show up. It can take a while..