I buy a vegetarian form of glucosamine. I do not want to use the shellfish product. Blue Bonnet makes one. There is also a liquid, Joint Juice, but it has sweetener in it. It's a generalization, but the great thing about youth is resiliance. I'm at an age where things start going wrong anyway. Add Lyme to that, and who knows? You are right, though, at 21, I'm sure it is particularly disturbing to be having what is generally thought of as senior citizen symptoms. However, you have a wonderful exhuberance that leaves me optimistic for your potential to get through all of this unscathed.
I have Lyme; it doesn't have me.