It’s worth reading this article. Sensitivities and intolerances are worth investigating. If you’ve been on a high-starch, low-fibre diet for years, you may be intolerant to certain kinds of carbs found in healthy foods (try reading about the FODMAP diet) and fibre in general. Sensitivity to things like eggs and dairy could cause bloating as well. You need to find out the triggers and eliminate them while you rebalance your intestinal flora and generally improve digestive health. Getting a check-up with your doctor certainly won’t hurt though.