The feeling..

I am 4 weeks and 4 days pregnant. I keep getting this feeling like I'm about to start my period. It's not really cramps (a little bit last night, but I heard that was normal and it went away). I have more that odd feeling like I might start bleeding or spotting. The feeling that's making me run to the bathroom and check for blood every 5 minutes.  I haven't had many symptoms, maybe gas. My nipples are sore in the evenings, but not right now. I had a chemical in January. Is this normal? Am I overreacting? First baby..