It sucks when you keep getting sick all the time. When it happened to me, I tested negative to glandular fever too, but a week later DH tested positive so our GP was convinced I had it too and it just wasn't showing up yet.

Vitamin C really helps with iron absorption too. So it's a good idea to eat something high in Vitamin C or take a Vitamin C tablet with meals and when you take your iron supplement. I have high iron and the Vitamin C makes such a difference to my iron absorption I can't have much of it.

I hope you get to the bottom of it soon and are back to your old self in no time.