period after pregnancy.

Okay so, I had my son 7 months ago, and I had my first period in October and then in December January. But then in February I didn't have one, in march I got my period. Now I'm almost through April and no period. And I'm am definitely not pregnant. Does anyone know if this is normal. Or what could possibly be going on. I've tried looking online but all there is, are questions unanswered and no questions like mine.