The dr did an mri and found arthritis in my lower back with degenerative changes what does that mean could my back get worse?

It is possible but: not certain, just like most things in life. If you have back pain the books by John Sarno, MD, may be helpful. Peace and good health.

PT evaluation: Great idea to get a professional physical therapy evaluation in addition to a medical opinion.

Progression is slow: In most of us time is not kind to the spine.At your young age it's likely that the MRI that found arthritis in your lower back w/degenerative changes is in an early & mild stage.Typically this does progress very slowly in almost all of us.That said,Physical therapy to strengthen your core is an initial important step.Pilates,ellipticals & swimming are great for maintenance.Work w/a PMR or spine MD