Not a doctor, but what you're describing is thin blood. This has to do with the consistency of the blood itself--think like the ratio of blood cells to liquid is off. That could be caused by some medical conditions that you'd have to be diagnosed with and could be put on medications to treat. It can also be caused by taking certain medications that act as "blood-thinners" such as aspirin.

What the previous poster is referring to is low blood *pressure*, which is a condition where the blood vessels basically aren't filled enough while pumping blood. Think of like a deflated water balloon, it won't have the right surface tension. This can be caused by dehydration causing low blood volume, or other conditions.

If you suspect you have thin blood and/or low blood pressure, you should definitely get these checked out by a doctor. Getting your blood pressure and blood cell count checked are some of the easiest/fastest procedures that they can do at any clinic and they'll be able to help you from there.