Help I’m so confused -

I’m on a bc pill with no estrogen since im breast feeding, and I have gotten my period.

My last period was about 2 weeks ago it lasted about 4-5 days.

These last 2 days I’ve felt very sick and nauseous. ( I’m not pregnant I’ve taken a test and it’s negative.) and I recently started bleeding again??

I’ve been working out more too almost 5-6 days a week if that has any reason

Any idea on what this could be??