short period concerns

so I'm on the pill and my period have always been consistent, lasting 4-5 days with days 2 and 3 being heavy. but this past month has been really weird. my period was 3 days late and when it came it was super light, almost spotting, it was so light. I'm not even filling a light tampon (tmi I know lol). it has lasted 2 days and now is ending. I'm just wondering has anyone had this happen and is it normal? I'm just hoping it was a short period and I'm not pregnant. I've taken 2 test and both were negative. I could be just worrying for nothing.