I would immediately re-establish care with your Bariatric doctor and voice your concerns with vigor. Tell them you need more than just a nutritionist visit, you would like testing to check on your anatomy.
To help with the dumping immediately try to really watch the sugar (and fat) content per serving in the foods/drinks you consume. Keep it as low as possible like your post op directions (I think it was 5 grams or less in my instructions)
Good Luck!