I need advice!!

I have pcos so my periods are never regular but I haven’t had my period since January. I have been taking tests regularly to make sure I’m not pregnant and they are all negative. I usually have a pretty flat stomach I watch what I eat and work out quite a lot. But for the past few days I have had a big round belly I don’t know from what and it’s started to be painful at times like really bad cramps. Has anyone experienced this? Any help would be appreciated!