Hi - sorry you have been so unwell. Obviously no one can rule out something serious but i hope it puts your mind at rest a little to hear that tonsillitis can make you VERY poorly and immuno compromised - especially when they become chronically infected. It used to be that if you'd had it 3/4 times in a year they took them out? Am presuming that is what the urgent referral is although am surprised your GP has waited this long to refer you. 

In my mid twenties i began to get tonsillitis repeatedly. I too was very small and i started to lose weight rapidly - i even got a ticking off by hospital staff who am sure thought i had an eating disorder! I was on constant antibiotics for 6 months and i felt constantly grim. As a child when i got it - i then used to get everything going as i got so run down so it could just be to do with your poor tonsils. I too have always had issues with my glands coming up and down, even from being a small child. I hope you get seen really soon and can only advise you eat as much as possible - anything and everything you fancy and can cope with x