Why do i get easily tired exercising now but before i use to be able to workout alot more then now?

about 1 month ago, i use to be able 2 workout for about an hour, running and bike, then i was sick for 2 weeks and now i try to go back to my usuall, but i just seem to get tired easily,
is it because i worked my body to hard back then?
also i weigh 179 and 5'9 and im 16 years old
Answer:
Mike, can I suggest you pop along to the doctor and ask him to give you a checkup? You may find the doctor will want to do 'bloods" (blood tests to check on whether you have a disorder). Now, if this is required, please don't let your mind race away with all kinds of ideas. This is a normal check and is not there to catch a nasty bug, but to, by process of elimination, rule out possibilities. The doctor will check for things like anaemia, dietary allergies, stress caused problems etc. The sooner you get checked out the sooner the problem can be diagnosed, repaired and go back to being a wild 16-year-old.

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