Hi Deejoy,
I haven't been able to breastfeed more than the first week. But I assume that it could be the same at 10 weeks. Breastfeeding makes the uterus contract and tighten up back into its shape before the pregnancy. I know that the more pregnancys you have the more painful the afterbirth pains are. I got most of my pain during or after bfing with this baby.

I think it could be your uterus getting back into shape.

Hope I have helped
Chris