Hi Claire
Sorry to go off subject slightly, but my son had GF in 2002, he was very very poorly with it, and had to be admited to hospital, he was 17 at the time, and it set him back a long way, the doctor told him it would be at least 12 months before he felt anything like right, and approx 18 months before he was back to a decent level of fitness, but he told him that it never leaves your system, and anytime you are run down etc it will start to niggle.
It could be this that's causing your jelly legs, or could be a small panic attack, which will trigger an adrenalin surge , which will give the jelly leg feeling, I know it's horrid at the time, i get panic attacks now and then, and I always get a lovely feeling of relief about 15 mins later when I realise I'm not dying lol
Good luck x