Super light period 2x this month. Any advice is appreciated

Hi. I'm 26yrs old and have always had irregular periods, except when I was taking BC pills. However, I've chosen not to take them anymore, and haven't since Jan '07. Anyways, I experienced a super light period at the beginning of July that lasted for about 5 days. I may have filled one entire tampon the entire 5 days. But now, I'm bleeding lightly again. I'm on day 3. I've taken like 5 pregnancy tests that have all proved negative. Does anyone know what this might be? My cycle seems to be between 39-46 days. My last normal period was May 30th. Then on July 5th, I had the 5 days of really super light bleeding and starting July 23rd I started bleeding lightly again. One other note to point out is that the first day or 2 of the bleeding has been browny type discharge. Now it's more reddish. Any advice on this would be appreciated! Thanks!! :-D