I'm sure many have posted and asked questions about this before, but I'm bleeding in between my periods. Not nearly as heavy as my normal period, but compared to regular spotting, it's relatively heavy. Saw a gynecologist today and I'm not pregnant, and she says it doesn't look severe enough to be an STD or anything similar, and the blood is too heavy for this to have been from having sexual intercourse. This is the first time this is happening, and it's a little concerning. What could have possibly caused this?