I'm new to this site as well. My IBS started up again (it didn't bother me for about 5 years) but came back after I had my third child. All of a sudden, I couldn't make to the doctors appointment or to the grocery store. I truly believe it can come on suddenly. Mine certainly did. I read that it can come on after pregnancy, illness, surgery, among other things. Preganancy really does a number on your body. The baby has squished all your organs out of the way and they have to bounce back. Its been 5 years now since my daughter was born and I've finally discovered that food is my greates trigger. Its been like night and day. I bought Heather Van Vorous' book "Eating for IBS" and its saved my life. Try it. It might help. But don't let your doctor discourage you. Good Luck and I hope you find out the info. you need.