Hey Elizabeth,
First let me say, I am enjoying your posts and I am so glad you are here. I have only had this disease for a few years. I am a total rookie compared to you. I am guessing you were not offered meds when you were first diagnosed as they weren't available. As meds came available you may have avoided them as you were feeling pretty good about managing those MS issues. If you have done this for 18 years, I would think you are doing just fine! Rememeber this, with or without drugs, this disease progresses. You are at a very typical age for your RRMS to transition to SPMS. Once you get to that stage, the meds aren't really going to help. Most doctors at that point take you off the meds as they are not longer helping. So if you think about it like that, you might as well stay the course. Talk to your doctor and see what he or she recommends.
It takes discipline to do this the way you have. There is no guarantee that you would have done better on meds. No ones knows these things yet.
My doctor wanted me on meds right away and pushed hard for that. I went with that but I also have made changes in my life style as well. I am at the beginning of my MS journey and it is way too early to say whether my choices will pay off with decent quality of life at the 18 year mark.
Well, that is my two cents worth. I really don't know if my post was any help at all but I felt compelled to respond.