There are many possible reasons for this. I suggest you check with your physician if the problem persists.
Blood sugar is probably dropping which would explain why you're feeling better after you eat.
you lose blood
If my thyroid T4 free blood results are dropping what does this mean?
Being able to feel very large blood clots, may be a problem. Feeling blood clots is normal, but large ones may cause vaginal viruses.
Normal blood pressure is 120/80 or below
It is normal for menstrual flow to contain the stringy black things you have described. They are probably small blood clots.
When you get sick, your white blood cell count is higher than normal your immune system, your white blood cell count can drop to very low levels.
Eating candy will affect a persons blood sugar level. If they are feeling particularly tired or dizzy, a bit of candy might provide relief and assist in bringing their blood sugar back to normal levels.
It's possible. Pressure on the blood vessels can reduce the feeling - when you shift position or stand up, normal blood-flow returns, and the tingle is the blood filling the constricted vessels again.
Just drops of blood no weird feeling
Being a diabetic- when your blood sugar drops-usually aroung 70 or so- and you get shacky or weak feeling- you need something sweet to bring it up to normal levels- the week, shacky feeling means your blood suger is too low!
The flow of blood through the body is what causes the sensation of little pin or needle pricks after exercise. The capillaries open and the blood flows faster than normal.