4 months post postpartum

I had my son about 4 months ago. I missed my period this past month. After I had my son I recovered quick. I bled for awhile I stopped bleeding for maybe a week or 2 but throughout that time I spotted then I had my actual period. I've had unprotected sex. Well neither of us have really fully finished. I haven't had my period all month long. My periods aren't normal. When I first got them I only had them twice a year (no birth control) I've been cramping,feeling like I'm going to start my period but could I be pregnant?