7 weeks postpartum and menstrual cramping?

I have been having very light cramping every day thinking I am due for my period soon, haven't had the first period since post birth yet. Yesterday I started my usual workouts that I did before pregnancy, long walks around 2 hours long every other day.  After I got home I ate and then later that night have extreme menstraul like crmaping but woke up this morning and they were gone and still no period? Anyone else experience this? Is it from working out?