Dizzy, legs hurt, shortness of breath, feel weird

For about a month now, when I walk even across the room, I get dizzy, my legs hurt, I feel a presure on my chest. I have low blood pressure (about 80/50 most of the time) I do have astma, but this does not feel like my normal symtoms. I walk to bring my grandson to the bus stop, which is not more than 50 yards, but uphill on the way home. by the time I get home I feel discomfort in my lower legs, my hands tingle, I feel dizzy.
It does not take much to have this happen. I can just carry my 20 pound grandson up a flight of stairs and when I place him in the crib, I sit on the floor for about 3 mintues until I feel myself again. It is scary.
any ideas?