Base of stomach's gone tight

Hi all, I have a question I'd like your advise on. Came off the pill on the 9th Dec for the first time in 17 years. Had a period (or what I understand to be a fake period as a result of stopping Microgynon 30) 3 days later on the 12th.  Last week I had stomach cramps. Not bad at all, but like the feeling you get just before you get your period and the base of my tummy went really hard. It's still like it 9 days or so on. It's not painful, but I've never had this before mid-cycle. According to Glow I've just finished ovulating (can this be accurate from month one after coming off the pill?) Anyway, I was just wondering if anyone else has had this? It's not painful to have sex or anything, but even sat here right now I can tell my stomach's tense. Have I just eaten too many mince pies? Ha ha. Merry Christmas by the way. Your thoughts gratefully recieved.