I don't want to scare you but I had glandular fever 3 years ago an it took 6 months to go It was awful, docs didn't diagnose me for months and I was so ill, at one point I thought it was all in my head! I was exhausted, had the sore throat, headaches, swollen glands, lost a stone (I'm only 8 and a half to begin with!). My mum actually started worrying that it was something very serious. So def go for your blood test, Im sure I made it worse by trying to get up and on with things like work, seeing my friends etc. If it's glandular fever you really need to rest and take things easy.
Saying that my sister had it a few months before me and hers was gone in a few weeks, just your luck really.