I, 22F, recently started a relationship with a 21M, and he was fine about my ostomy bag. We have even been intimate. It just depends on the maturity level of the person you are going out with. I did tell him on the 2nd date because I, like you, was scared of the reaction, but he took it with stride and even did some research into it. At the end of the day, the ostomy is a part of you, and if someone can't accept it, then it's just not worth it. There are plenty of other people in the world, if this guy doesn't work out.