Breastfeeding & pregnancy. Is it possible?

So I'm 3 months postpartum & exclusively breastfeeding my baby boy. He has been sleeping 7-8 hours at night consistently since about 6 weeks. I had a little bit of spotting probably 6 weeks ago, and nothing since then. I've been waiting for my period to return since I'm no longer nursing around the clock, but it hasn't yet. In the meantime, I've assumed that no period = no ovulation and haven't been using any protection other than pulling out. Now I'm feeling a little nauseated and dizzy and hella crampy. I'm kind of freaking out wondering if somehow I got pregnant. Someone please talk me off the ledge here, it's super unlikely right? Probably just my body gearing up to start having periods again right?