Actually, not everyone you see around you is healthy and fine. In any crowd, there are other people that are sick with something. Maybe something as common and temporary as a cold or allergies, while some might have cancer or an eating disorder. You are not the only one that suffers; other people are just as adept as you are at pretending to be normal. And they probably feel just the same--that they are not normal and everyone else is.
IBS is on the rise in western countries, whether from diet or just more people willing to talk about it and more doctors willing to recognize it as a real problem. More likely than not, you already know someone who also has GI problems, they may just not have said anything to you about them because of fear. When someone I know makes even a slight comment about any sort of gut problem, I open up about my own problems. This makes my own problems seem less, and everyone else tends to discuss their problems more in depth and with relief that someone understands and doesn't judge and can even pass on helpful tips. I then add that person to my mental list of people it's okay to be sick around because they'll understand. The more people you have on that list, the easier it becomes to socialize because you don't have to worry about pretending to be fine when you're not. And, oddly enough, when you don't have to worry about getting sick, you have a tendency not to get sick.
You have a lot of things you want to do in life, but fear of IBS is getting in your way. I would suggest adding something else to your list of things to do--something that you should do first: found an IBS support group. It can be as simple as inviting people into your home once a week just to talk. It's okay to talk about gut problems in detail (just like we do here), but it's also okay to talk about things which are mostly unrelated--work, kids, love, hobbies, etc. It can be both a place to share your problems and a place to just socialize like normal people without being afraid of ridicule or condemnation. They won't care if you have to go to the bathroom or step outside to fart. They will understand if you don't drink or eat at all, or at least certain things, because they will also have their own personal list of no-no's.
Most all local newspapers have a section where they list local activities that are going on during the week; it won't cost you anything to advertise an IBS support group meeting there. You might also make up a flyer for your doctor or GI's office and let them know that you are organizing a support group, so they will know to suggest it to patients. You may be surprised by the number of people who show up.
I think you would find, if you had other people like yourself to socialize with, you wouldn't feel so alone and you would take strength from the shared experience and be able to handle other social situations better. I know that my attitude towards my bowel problems has changed since I got on this forum. Talking about bodily functions used to be embarrassing; now I don't have a problem talking with other sufferers at all. And when it's easy to talk about, it's also easier to deal with. I don't get nearly so uptight when I have a bowel problem now. I take some medicine, wait near a toilet for about 30 minutes, then go on with my day as if nothing ever happened.
A couple of years ago I went from the U.S. to London and Scotland for two weeks. My guts got upset because of the travel, but I figured out quickly to skip breakfast; I would let my husband go get something to eat while I stayed in the hotel room, pooped, and took my medicine. By the time he was back, I was usually ready to go sightseeing and was fine the rest of the day. That didn't last quite one week; by the time we were in our rental car and driving all over the island, I was good (I was even able to eat breakfast sometimes). Which was good for me, because it's a lot harder to find a bathroom when you are traveling in the U.K. than in the U.S. But if I had let myself get really upset over my initial problems, they would have never gone away and then I would have had problems in the car.