PM, it could just be the pg hormones leaving your body - that takes about 3 months to happen fully. Or it could be your cycle starting. Or you could be pg. I know that's not very helpful, but all I'm trying to say is that what you are describing is not abnormal at this stage.

In terms of contraception, bfing is considered 98% effective for the first 6 months post partum, only if you are exclusively bfing (no formula or solids) AND you are feeding during the night AND you don't have AF. But there are a few mums on here that have fallen into the 2% so it is possible. You don't have to have AF to start the mini-pill BTW, so if you aren't pg and don't want to be then maybe you should consider starting. This of course is entirely up to you and your situation. I couldn't take the mini-pill but didn't fall pg during the first 6 months either time without any other contraception.

In the meantime, consider a HPT or BT to be sure. Good luck, I hope you get the result you want.