What is hypermobility?

I have some questions about one specific condition that is troubling me for years now.
I'm 55 years old and I have big problems with my joints.
I am suffering from recurring pain in numerous joints. I know that this couldn’t be some type of rheum because I think I'm too young for that.
I have been to many doctors and I came out without a definite diagnosis or helpful treatment at all.
Recently I have heard something about some disease called hypermobility and I was wondering what kind of disease this is and what are the symptoms of it?
Thank you in advance!

Because my son is a medical student, I asked him to tell me something about this disease and here I am and I want to help you.
Connective tissue proteins such as collagen give the body its intrinsic toughness.
When they are differently formed, the results are mainly felt in the joints, muscles, tendons, ligaments - which are laxer and more fragile than is the case for most people.
The result of this is hypermobility and vulnerability of joints.
Several diseases like rheumatoid arthritis, osteogenesis imperfecta, systemic lupus erythematosus, poliomyelitis and myotonia congenita
could cause your condition.
There is no known cure for this disease because it is still a mystery.
HMS patients must be educated about their body mechanics, posture and activities because activities may have to be modified.
Strengthening exercises and balance boards for proprioceptive stimulation are recommended.