What’s going on here!

So. I’m 7 and a half months postpartum.

My cycles returned at the end of January. I know they can be pretty wonky at first when they are getting back to normal.

I’ve had brown spotting for the past several days. Just small amounts when I wipe.

The past few days I have had nausea, some irritably, headaches, and most recently my nipples have been extremely sore when nursing.

I started taking opk’s a few days after my period ended. I have not gotten a positive.

Totally have no clue what my body is doing. Any thoughts? (All tests have been negative thus far and no confirmed ovulation to know exactly when I would have ovulated.)