Help please very irregular menstrual cycle?

hello i have been having very irregular periods for 9 months it all started in may when i started to have very light spotty periods to where all i needed was a panty liner. And for the month of june i spotted for 2 weeks straight, then for july, aug, sept i had the very light spotty periods again for the normal amounts of days. And for the month of october i had a regular flow period so i thought things where back to normal but i was wrong i have now missed two months of my period in a row no spotting or signs of a period at all. I have tooken home pregnancy tests and they are all negative. me and my husband have been ttc so for about 10 months so i thought that it could be possible that i am pregnant but the tests are negative. so does anyone have any ideas what it could be? i have an obgyn appointment in the morning i am just wondering if this has happened to anyone else? and what ended up being wrong.