Fed up...constant digestive issues

Hi all,

I have been vegan for just over two years. During this time I have had good and bad periods but have never gone off track, and haven't eaten any animal products.

However lately (past 6 months, but less severely before this) I have had problems with gas, bloating, frequent 'toileting', noises etc. This is incredibly annoying in social situations especially college (UK, so probably high school to you Americans).

I am a 16y/o male, 6'0. I eat 4000-4200 calories a day with around 200g protein, 160g fat and 400g carbs. Usually I have around 3-6 servings of fruit veg, one servings of beans a day and a decent amount of bread, pasta (wholemeal variants) nuts. I take a omega 3 supplement and drink a litre of soya milk a day - a cheaper brand with no sugar etc providing B12.

I am a MTBer and am also on starting strength, making OK progress but I also feel like this diet is holding me back. I an gaining weight steadily but at a good rate.

Any help would be appreciated. I want to stay vegan for ethical reasons but the more reading I do and the longer I feel like this the weaker my willingness to stay vegan gets.