Am I sick? Exhausted all the time?

I'm a 14 year old girl and I am so tired all of the time. Not necessarily like before bed it's just when I got a tiny bit sleepy at all it like magnifies until I physically cannot keep my eyes open. I find it impossible to get out of bed it the morning more than normal, when I do get up every fibre in my body screams at me to go back to sleep. I'm also experienceing dizziness when I stand and shortness of breath sometimes. I had glandular fever a year and a half ago or more if that makes a difference (also lymph nodes on neck but I think they are from the glandular fever) please help X