I wasn't officially diagnosed until I was 39. I have suffered since early 20's but really rather mild until I had a hysterectomy when I was 36. After that my IBS was worse with the attacks more frequent.
I grew up with my Mother having attacks and rushing to the bathroom. I thought it was perfectly normal for the same thing to happen to me. I remember my sister and I going into a store to pick up something, I think we were 11 and 13, while my Mom waited in the car. When we came out she was gone. She had to rush and find a bathroom. She did come back a short while later though, LOL!