Here is some information about low pressure from the School of Natural Healing Book:
Insufficient blood pressure for normal circulatory and nutritive activity.
Low and high blood pressure are both due to malfunction of the circulatory system. High blood pressure in many cases works just like low blood pressure. Cholesterol must be eliminated from the system in order to get the blood flowing more freely. The condition is brought about by improper diet, insufficient rest and exercise and a lack of vitality within the system.
More oxygen is needed to correct this condition. Garlic is a good oxygen carrier. One of the greatest aids for low or high blood pressure due to oxygen starvation is deep breathing which serves as a catalyst and helps the herbs act more rapidly. An immediate increase in circulation may be obtained by the use of cayenne and non-mucus forming foods. Grape juice as well as other juices rebuild and give endurance to the system.
Blue cohosh, burnet, cayenne, gentian, golden seal, hyssop, prickly ash, red pepper, sassafras, vervain, wood betony.
A personal thought: have you been checked for anemia? This condition will normally make one have a lack of energy because of oxygen-carrying red blood cells.I hope this helps.