5 1/2 postpartum... weird periods?

Anyone else this far out and having irregular periods? I stopped breastfeeding when my son was two months old(in December). I had a first real period back in December. Had like two periods in January. Period seemed normal on February. No period in march. And because I'm not on birth control I took a pregnancy test just to rule that out, so not pregnant. I've been feeling a crampy sore feeling as if I would when I'm going to start my period but nothing. I would've had my period like the first week of march. Wondering if this is normal?