I do not not have any knowledge about your sons symptoms. However I speak as a mum and I feel your frustration, please keep chasing up the appointment with the haemotiogist. Ring every day, Ask questions, speak to someone higher if you can, go to another GP. You have to be persistent! My son has been diagnosed with a rare form of bone cancer in January . He had hurt his leg playing football and his symptoms came and went over 6/7 weeks. I didn’t trust the Drs surgery as it was Xmas time and his first GP didn’t even look at his leg! instead I sat in A and E and asked for an X-ray (no real reason for doing this, I just felt as a parent that something  wasn’t right). From that night everything happened very fast and my son was diagnosed 23 days later and treatment started immediately . I am not angry as I bypassed the GP ( thankfully). I have come across many parents who were visiting GPS and A and E for months, sometines over a year before they were listened to and their child diagnosed with this rare bone cancer.You must be persistent - you know your own child. I hope everything is ok, but it is best to have things checked and quickly. If you have any questions please pm me. 

I don’t mean to scare you, I can feel your frustration and as parents we want to do everything we can for our children. Wishing you all the best and that everything is ok. It is best to rule out worst case scenarios. My son only had pain, no other symptoms and he continued to work and play football during those 6/7 weeks!