sickness.... any ideas?

thanks.

am still a bit confused but will probably go back to the doctor if it gets any worse. (i think the doctor's getting sick of me )

hey... i'm getting a bit worried as i seem to be getting a recurring illness.
in about march... over a course of a few days my nose had started bleeding quite a lot... (i don't know if this was linked to me later being sick) then for about 3 weeks i was just really not feeling myself. i was almost always dizzy and had a splitting headache, and no energy. this got worse and worse over the weeks until finally i ended up in bed with no energy. one night i started throwing up and didnt even have enough energy to kneel by the toilet to throw up. my mom called the doctor but i over a few days i got better and gradually regained my strength.
about a month later, i began to get the headaches and dizziness again so went to the doctor who said i was probably only just getting rid of the bug... and gave me a heap of paracetamol.
this went away again... only to return again...
i'm not sure how many times i've had it but i was getting it during my exams, which i put down to stress...
thing is i seem to be getting it again... each time i get it i just hope it doesnt get as bad as the first time when i was being sick and was bed-bound.

does anyone have any idea what this could be?? or what could be causing it?
it's not stress!! it might have been during exams but the rest of the time it definately wasn't... especially now... i couldn't be less stressed!! my exams are over, i've finished my last year of school and summer is setting in.

if anyone would have any advice at all i'd be very grateful!!
thanks.