The different stages of MS disease process and symptoms even though stable

Hi. I was dx with RRMS in October 2012. Began with an injection then a pill now in an infusion since July 2018. MRI's come back as no new lesions, MS is stable.

My question: can a person remain in the RRMS stage for the entire duration of their life?

Also, how can I still experience worsening of my symptoms but zero evidence of lesions??

Thats what confuses me.

Thank you 😊