BF and severe period like pain but no period

[An89]

DS is 10 weeks old, I BF for 2 days in hospital but then due to issues I went to formula. I then reintroduced bf and began combi feeding when baby turned 5 weeks ... he has around 2 bottles / day and the rest is bf.
I've started getting really severe nausea and cramps which feel like period pain but no period, is this normal so late on into birth? (Definely no period coming)

They could be "ghost periods". I found my body practiced having a period before actually having one, if you get what I mean?

As usual though, Kellymom explains it much better than I ever could