A doctor would be able to do a blood test to see if you were anaemic and required a supplement of iron
. Folic acid helps with the absorption of iron
Foods rich in iron are liver, kidneys, dark greens, cereals are fortified with iron. You may find more.
Like you mentioned asthma - you would have a persistent cough too with that and gasping for air. The doctor can do a simple lung function test at his surgery to find out whether you have become asthmatic or not.