I am pleased to welcome you to Living With PsA! Thats an awesome collection of hobbies you’ve got there - I’m sorry to hear that your conditions has interfered with your regular lifestyle. In regards to your question about the side effects of MTX treatment, hopefully some members will reply to this post, but I also used the Search icon (top right of white bar) to look through previous topics that have mentioned this.
These are the results I got from searching “MTX side effect”:
https://discussion.livingwithpsoriaticarthritis.org/search?q=MTX%20side%20effect
Hopefully that provides you with some useful information. Otherwise - I wish you the best of luck and encourage you to ask me any questions that you may have!