I'm a competitive swimmer and use to train eight times a week but I've dropped down due to tiredness and aching knees and hips. Also experience chest pain and become really breathless when I train but I don't have asthma. Also had glandular fever a year ago. Had a blood test and iron levels were 14 and sats were 22% took iron supplements then went back and iron levels had dropped to four and sats were 7% Any ideas?