Ah, you'll get use to it. I kind of have a small advantage, when I first started playing all those years ago, my buddies and I were so broke we couldn't afford the expensive stuff, so we started off using bb guns. We got tired of waiting around to play every time we got hit, so we stopped counting hits and started making it so you had to actually capture your opponent. So, all of us that played back then had to take hit after hit, and we didn't have minimum distance rules either.
So, after playing like this for 20 years, many of us, myself included, we just got use to it. Now we play with real airsoft guns, we stand there shooting or getting shot and it doesn't really phase us anymore. Yeah, we'll cuss about the pain or getting hit, but we just keep on playing. It sounds crazy, but that's how I developed a tolerance.
I'm not saying you need to follow my footsteps, but eventually you'll find what works for you. Pain is truly in our minds after all, so if you learn to ignore it or accept it and then move on, it gets easier to deal with as you go.
Good luck with your costume, if you have any pictures of the character I can probably help you figure it out, I'm kind of good with that kind of stuff. Check out my Batman costume thread in my signature.