I am 27 years, and have regular sex these last 3 years. I am facing some differences in my periods even though they come once in 28 days. These last 3 months they are very dark red color (looks as black) last only 3 days, followed with only head and breast ache and what mostly bothers me they flow only as in big pieces . My urine, general blood report is OK. I have also made an echo and that is normal too. Do I have to get worried?