Weird period

Please help if its happened to you. I had my period since i was 9. Im 33 today and have always been regular 28, 29 days. I have 3 kids, youngest is 11. Been ttc for about a yr. this months period was 7 days late and when i got it ita been off and on. Pad is clean from morning to like 6pm then ill spot or get a regular flow then stops again n continues. Ive never been late other then 3 yra ago i was 3 days late but due to stress. I took a pref test and bfn. Can someone ease adv if this has happened to them?