Hello everyone this might be nothing might be something....

so for months and months now my 2 year old son has had swollen glands in his neck and groin which never go down he doesn't get ill much so I know he's not fighting like a viral infection or something. He then began limping on his left leg which he still does this has also been going on for months,he complains sometimes that he can't walk or can't ride his bike and gets really upset. He's also been really tired all the time falling asleep randomly which is really unlike him as he will only sleep in his bed! A few months ago he also started sweating excessively when he went to bed and still continues to soak his pillow and bed every night. He's been pale a lot of the time and I feel like he looks thinner as his nappies are looser now and he feels skinnier. But he had his weight checked and he hasn't actually lost much. He's been refusing meals for a while now though I think this is just a phase he's going through as he says he wants other things such as sweet treats so I don't think that's to do with all of this. He's been on and off for weeks some days he's completely fine his normal self other days he has funny episodes then he's ok again! He's been sick tonight and has started coughing bad and gasping for air at one point (this only happened once) when he woke up from his nap. I've taken him to the doctors several times where they say he's fine they do his temp and physical examination he's had a urine test which came back clear also. I have requested that I want blood tests doing several times but they refuse saying it's unfair to do it to him when they think there's 'nothing wrong with him' I just don't know what to do anymore as I feel I'm getting no where but deep down I know something isn't right at all. I'm getting worried as he had lots of symptoms for Acute Leukemia and I've read stories where some children who had it started with a limp and things like that but I just don't know what to do anymore!