I am a yellow belt in Tae Kwon Do and I also have a couple of years experience with Karate and shaolin-do. We have a tournament coming up and it's the first I've ever competed in. My problem is that I have general anxiety disorder (with a bit of Agoraphobia) and being in that situation is really something I'm worried about. I do take zanax for the anxiety, but I will be sparring and I would imagine that that medication will greatly impact my performance (can either give me a 'buzz' or make me fatigued). Of course I really need to be at %110, especially since I'm 41 and I agreed to enter the 18-39 division at my instructor's encouragement. I am not worried about my performance or skill level when sparring in class, but I fear that without the meds I wont be able to concentrate on the match at the tournament, just everyone looking at me or worse, just back out at the last minute. Maybe I should just try a half dose, but it will still effect me. Anyone else ever in a similar situation?
I can't say that I have your exact experience, but I have Diabetes and take medication for it and spar in tournaments sometimes.
The most important thing is to understand your medical condition, as others have said. Don't put yourself in a situation where you might get hurt.
However, after that, perhaps I can add a couple things that might help you.
Have you been to a tournament before? If not, you might benefit from actually seeing what a tournament looks like. The sparring, especially at your level, is no big deal. At your age and belt color, you may find there is no one in your division anyway; they you either win automatically by default, or they put you in a different division.
Take a look at similar sparring on Youtube, you might get an idea what it looks like at YOUR level (don't look at black belt level sparring)
In TKD and most other styles, you'll be wearing protective gear and you'll be point-sparring. So it's one point and stop, one point and stop. It's over quickly win or lose.
There is no shame in losing. People who compete have already won in the sense that they have the guts to step into the ring. When I lost my first several tournaments (and I'm over 50 years old), one of the younger people in my dojo had something to say about it, and my sensei stopped that cold. He said "When you have the guts to step into the ring, then you can talk about how other people did in competition. If you haven't got the guts to do it yourself, you have no standing to say jack to anyone else, whether they won or lost."
Consider it a learning experience no matter what. If you lose, you learn, if you win you learn. Learning is good.
Relax, enjoy. Some of the nicest people I've met in martial arts so far outside of my own dojo were people I sparred with. We've become Facebook friends, we like each other. We share a common bond.
Good luck, be safe, and have fun.