Hello. I am 18 years old and healthy. I have somewhat irregular periods that are generally heavy with very prominent pre-menstrual symptoms, such as tender breasts and heavy cramping. I got my last period on July 16th, but as my periods are quite irregular, I didn't really know when to expect my next one.

Yesterday, I suddenly started bleeding. At first it was a light brown filmy consistency, then it became very heavy and dark brown, and then gradually started moving into a reddish color, almost looking like true period blood. This was over the period of one day, and after checking this morning it looks like I am still bleeding with that consistency. The strange thing is I had minimal to no warning of this bleeding, so I have no way to know if this is my period or not. I had no tender breasts, no mood swings, and minimal cramping the day before it started and during the bleeding yesterday.

Can anyone tell me what this is? It is not likely I am pregnant; I have never had sex before, but I have had oral and manual (no genital-to genital contact) sex with my boyfriend about two weeks ago. We are always careful.

Thank you for any input!