@georgeeliot, I'm 77 today 🙂 and also in the high risk category with an autoimmune disease but it's currently in remission so I'm not taking any medications. I'm not sure anyone can answer your question even the doctor (IMHO). I think the real question is which is the worse risk - stop taking the methotrexate and a new risk of what occurs when you do that or continue taking it and the risk of getting an infection from COVID-19. Here are a couple of articles that may provide a little information towards what you are asking.

COVID-19 infection and rheumatoid arthritis: Faraway, so close!: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7102591/

Methotrexate and Coronavirus: Does Methotrexate Make You High-Risk for COVID-19?: https://creakyjoints.org/treatment/methotrexate-immunosuppressing-coronavirus/