So I don't have periods very often, but when I do(usually every other month-irregular) there are…

So I don't have periods very often, but when I do(usually every other month-irregular) there are extremely heavy. This month Ive been having a very light pinkish/brown spotting/bleeding for the first time. It's been maybe 5-7 days and it seems to be stopping. I've taken pregnancy tests and even went to the doctor and they were all negative..... I really don't know what to think..