Joints feel like they're loose and then cause pain. is this arthritis? what can it be?

Possibly: There are two types of arthritis - inflammatory and noninflammatory. The inflammatory ones are those caused by rheumatoid arthritis, lupus and gout and some other ones. The major cause of the noninflammatory arthritis is wear and tear or osteoarthritis. Also, fibromyalgia is a "buggy" nowadays, especially in females. Signs of inflammation include redness, heat and swelling and pain.

Not usually: Arthritic joints usually feel stiff and painful; typically not “loose”. There are patients who have hyper mobile and unstable joints for a variety of reasons that can cause pain and loss of function. Don’t hesitate to see a specialist to discuss the specifics of your case.