Help Postpartum craziness !!??!!

So I'm 6 months postpartum and I started my period about 4 months ago. I have had a period every month for the past 3 months, this month I am 2 weeks late. I am experiencing twinges and lower abdominal pressure. I feel alittle different physically, I just don't feel normal. Is this normal to feel during postpartum phase? I took a test about a week ago and it was negative. I haven't taken one since because I don't want to worry myself about wasting money on a test if it is negative.