Sometimes you can have an extended time where the mind-body aspect of IBS goes away after using the hypnotherapy, and then it returns. This happens at times due to what is called 'shadow fears' and over time, will usually go away.
You may want to go thru the hypno sessions again if you can and many times this will help reinforce the new neural pathways that will help you dis-associate travel, exams, leaving home, etc. with IBS attacks.
Also, reading, writing and 're-living' anything regarding IBS just reinforces it for some people - tho I know it is hard not to look for support, etc. so it is understandable. But at some point, it may be something to consider so you can break the connection - it can be done as you have shown, so please do not get discouraged by this - many folks have gone thru temporary relapse from time to time - dont give up hope! Hope that helps... all the best to you.
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Re: examination and ibs..
Hope that helps... all the best to you. 
