I would agree with Dr Bungay, a dietitian can be very useful to help you find out what the problem is with foods, you would need to have coeliac disease tested and do need to be eating foods containing gluten to ensure the test is positive please check out the following document
http://guidance.nice.org.uk/CG86/PublicInfo/pdf/English
As foods that are high in FODMAPs, or fermentable starches, are generally those foods that also contain indigestable fibre - good usually for diabetes, a dietitian will be helpful to help you tease out those foods which will help both your bowel symptoms and enable you to have a good diet for your diabetes.
I am in the process of writing a post about travel and IBS, you may find some of the following advice useful
If flying, book your seat in advance as near to the toilet as you feel comfortable with. Don't forget your Can't Wait Card (just having this with you can help with the stress of travelling and feeling anxious about needing the loo quickly - being anxious about this problem isn't helpful to IBS symptoms) and keep it in your hand luggage. You can get one from The IBS Network
http://www.theibsnetwork.org. You could also mention your needs to cabin crew, they can often help you to access toilet facilities quicker, if you don't wish to let them know on the day, call in advance.
If you suffer from food intolerances, booking your in-flight meal in advance: contact the airline and discuss your needs with them. Take snacks in your hand luggage to ensure regular meals. For followers of the Low FODMAP diet, or those who exclude any other foods, avoiding foods that result in symptoms at least 48 hours prior to travelling.
Contacting your hotel to discuss food requirements before departure is useful or perhaps going for self catering if you have more than one food intolerance and would find it difficult to manage otherwise; often plain food such as rice, chicken & fish are common, so are worth considering.
Equipping yourself with medications such as re-hydration salts is useful, keep them in your first aid pack, as you can become dehydrated very quickly, especially when experiencing diarrhoea. Generally ensuring you drink plenty of fluids: 8-10 glasses per day are usually adequate but you may need more - dark coloured urine is usually a good indication that you are not having enough.
But most of all enjoy your trip - some people find that a holiday is a very good idea for your IBS!