Period Symptoms?

I'm 5 weeks 2 days and I should be on my period around this time. I'm 16 years old and I've been trying to convince for about 4 months (long story) the point is that I'm irregular sometimes I get my period sometimes I don't. I tested 5 times and all were positive. I keep on having this feeling of getting my period not cramps but a heavy feel in my lower stomach I always feel this way during my period.  My question is if it's normal to feel this way? Has anyone else had the feeling of getting your period during early pregnancy?