Unfortunately it's not uncommon for HD to go undiagnosed or be misdiagnosed. Try not to get too upset though because there are other diseases that your father might have which are not hereditary.
In the early days of presymptomatic testing, facilities and doctors followed strict protocols and it was hard to get them to agree to test someone for the HD gene whose parent had not tested or been clinically diagnosed. These days, you can find a doctor who would test you and a lab which would agree to do it.
You might want to think though before you do this. Going through testing is a very stressful time and many people benefit from some counseling beforehand. It's also a good idea to make sure you have health, life, and long term care insurance before testing in case you do have the gene. We have articles and links on our FAQ pages about testing that I think you will find helpful.
I wish there was a way for you to find out more information about your father's condition. There might be a clear diagnosis of something other than HD that you just haven't been told about. Perhaps you could go with him to his next doctor's appointment. I do understand about family dynamics though.
I wish you the best of luck. I'll be thinking about you. I hope you will keep in touch.