I have knee pain and I'm only 20. Does that mean I'm going to have a ton of problems when I get older?

Not necessarily. Do you recall any specific trauma to your knee, or did this just come on spontaneously? Does it hurt all the time or just with certain activities? Have you tried ice, heat, and/or anti-inflammatories? If you have not, you can try that first. If it's a constant pain, then you should consider seeing an orthopaedic surgeon for a physical exam and x-rays.
Not . Necessarily. Work on strength and balance of strength..And get evaluated.