Menstrual cycles are not the same each month. One time there can be heavy vaginal discharge and the next time there would be light bleeding. It is normal to have some blood clots during the monthly periods but it can be a matter of concern if it gets intense along with other symptoms like fatigue and abdominal cramps.
Blood clots can be part of vaginal discharge during menstruation. Quantity of vaginal bleeding varies from one month to the next and also it varies from one woman to the other. Several factors can influence the intensity of vaginal bleeding including metabolism, number of RBC and general health condition.
If you are passing heavy blood clots in your periods, it is definitely a matter of concern. You need to consult your doctor promptly if you have such heavy bleeding with plenty of blood clots. For many women few blood clots can be present in the first day of monthly periods and not on consecutive days. Heavy bleeding and intense blood clots can be due to underlying problems. Several factors like anemia and intake of hormonal drugs can influence the rate of vaginal bleeding.
Having monthly period indicates that you are healthy and your reproductive system is good. It is a definite sign of the process of ovulation and secretion of sex hormones like estrogen and progesterone. It is true that some women (or most of them) may have premenstrual syndrome and other signs like headache, mood swings, depression and fatigue before the onset of period which gradually disappears on the first or second day.
Ovulation
Ovulation is the process during which certain hormonal changes stimulate the ovary to produce an egg. Ovulation happens about 12-16 days before the next monthly cycle starts. Eggs are normally stored in ovaries and one of the eggs is released from the ovary which is fully grown and ready for fertilization. During this process plenty of estrogen is produced and the uterus prepares itself for the fertilized egg by making a thick inner lining of endometrium.