Can I be pregnant again?

So ladies I have a question, I had my baby girl 4 months ago (1st child) and it was a vaginal birth, I bleed for 8 weeks after having her. After that I have gotten my period for 1 week every month. I'm breastfeeding only. I heard of moms that breastfeed and don't have their periods, but so far not me lol... last month my period came for the 1 week, than after 2 weeks I had a light bleeding for about 4 days. Than this month I didn't get my period at all. I have been cramping and I thought it was going to come and nothing. Me and my husband had unprotected sex. I'm debating on taking a pregnancy test. Has this happened to anyone ?