Unusual cramping

Hannah
My husband and I just started ttc this month for #2 I had a period in the 28th and ended in the 31 of March. I haven't had a period in about 2 years cause I was Breast feeding for a year and then I began continuous birth control to help with my ovarian cysts. I am using opks and have been since the 3rd of this month and have had some with a faint line but not as dark as the control line so I don't think I have ovulated yet but for the past 3 days my uterus feels heavy and full that's the only way I can explane the feeling. And now today I have been having cramping in my uterus, idk if I am getting used to being off birth control again or what but it sucks, anyone else have something like this?