I, like Cestamy, have endo, so my periods are super heavy (like super tampon every 30-60 minutes during the worst days) and lots of clotting. Very dark, very heavy, very crampy. Even without endo, I thought menstrual blood was dark, but IDK! Have you mentioned this to your OB/GYN? It could mean your endometerial lining is too thin, or it could mean nothing! If you don't mind me asking, how old are you? It could be early menopause symptoms, so I'd definitely talk to your doc so you don't miss out on your fertility window. I do NOT mean to freak you out; I only mentioned it because you said your periods used to be darker and heavier. HTH!!