Mate, I had Glandular Fever when I was in my last year at Uni and it is a total arse of a virus. It is does not get the general attention as it should as people who have not known someone with it, think it's just like the flu or something. I lost 4 stone and was knackered all the time for 3 months. This for a mad sportman who hates doing fu$k all, all i could do was go back home and sleep and chill out.
I totally sympathise with your work situation, the GF will have a side effect of making your stress levels heighten and lower your natural ability to cope with day to day shite.
I would echo the comments made, get your GP behind you, get the Employers Personnel dept. in the picture and cover yourself.
You will make a full recovery from this. The only extra advise I can give (from experience) is do not get pissed. You will screw your liver up and become a cheap nite out dude ! On my first night back to Uni, after the Doctor had warned me not to drink excessivley, I did and woke up at 4am in a city centre flower bed. Normal 'rugby lads' nite out then .... lol.
I hope your year improves matey ..... don't let the wankers get you down, its just not worth it longterm.
Dave