Postpartum spotting and breastfeeding

My baby is 3.5 months and i started spotting and cramping plus a random hot flash two days ago, today is day three. I took two pregnancy tests last night and one this morning and they were negative (we had sex like two or three times when i initially ended with postpartum bleeding at around 8 weeks, but we aren’t ready for another so we’ve used condoms since.)

Is this normal? To be randomly spotting like this? It’s sooo faint and reminded me of when I got pregnant which is what made me take the tests.