Missing period but not prego?

My husband and I had our first a year ago. My cycle returned to normal in November. We decided to start trying again in February. I had my period in feb and March. We did what we needed to do in March when I was ovulating. My period is now 5 days late but I’m getting negative results. I’ve literally NEVER had a late or missing period except for when I was pregnant. Any ideas what the heck is going on?