Cramps but not having periods.. Nexplanon

Tamara • Married to the most amazing man, have the most beautiful little girl and handsome baby boy. So completely happy with my life!!
I've got the Nexplanon rod, it was put in, in November. I had one period at the end on November and not since. Is it normal to of been having cramps and feeling uncomfortable like I should be coming on? I've been feeling like this for weeks and it's starting to bug me!