Crystal,
My daughter Hannah was like that. After 6 months of living at counts btw 3k-10k, when I gave her the right homeopathic remedy for her, she went up to 411k in a few days and has stayed in the high 300's consistently since then--8 1/2 years ago now. To my knowledge, she has dropped only once. That was when she took a blow to the temple in an obstacle course and she got inflammation of the Trigeminal nerve. It's also known as the "suicide nerve" because 30% of succeeded will commit suicide because the pain is so intense and so unrelenting. This was an instance where I took her to the ER when I couldn't seem to find a homeopathic remedy to help. Fortunately, I found a very high potency of her usual remedy in my travel bag at the ER, that I'd been looking for earlier. It literally stopped all her pain within 3 minutes! But, since we were there, they did a CBC and her counts were 50k. No surprise, really, as it had put her body under so much stress.
But, the important thing is, they had her come back in 2 days later and after having one more dose of her remedy, her platelets had bounced right back to normal. Everyone's platelets-whether they have ITP or not--will have times when their platelets or other blood cells will fluctuate. Our bodies are dynamic organisms--not static. There is nothing dangerous about going up and down a bit as his body will roll with the punches of life. The body's ability to right itself, to come back to homeostasis, is what you want to see. As a young child he will definitely have some illnesses and accidents, and that is all well and good, as it is the main way that his immune system will grow strong.
Also, why do you say he had no treatment, when you were using homeopathy on him? According to you, it completely changed his behavior for the better, he was looking good physically, he had a big growth spurt, he healed very quickly even after a huge head bonk--and now his platelets are going up too! I do think the homeopathy was what has been helping him. Either that, or just a lot of spontaneous healing going on.
Anyway, if he can go up once, he can do it again. Important thing is to avoid drugs and toxins that can overwhelm his body's ability to break them down. I see exposure to these (even seemingly benign OTC drugs), to be the #1 reason forITP relapses, in my experience.)
There ARE many safe alternatives. I've managed to raise six kids, half of them adults, now, with never resorting to antibiotics except for one, when he got an overwhelming sepsis from a MRSA infection he contracted during an operation after an injury. My kids are clueless as to even what an OTC drug is--they know the Homeopathics work and work quick. Of course it's not the only way to treat things, but I've found it to be a good way. Just saying there are alternatives to drugs.
In regards to when do you stop worrying, I think that's pretty normal. Probably not until his counts are normal for at least 6 months. For me, anyway, that was the magic number. Maybe it was because that was when they released us from having to come in for counts unless we saw symptoms. Of course, you'll have it harder, I think, being that he's a boy, as there does seem to generally be a difference there in the level of activity and the degree to which they like to scare the pants off their moms! Just ask Dougie's mom...