I suggest that you take a magnesium supplement - try Salus Haus's Floradix magnesium liquid, taken with your dinner in the evening. Also, take 20 drops of Digestisan tincture in a little water (e.g. a tsp) before breakfast and dinner. Between them, these should start to reduce the irritability of your bowel.
I'd also like you to be very careful to avoid all fried foods, and anything fatty like crisps, biscuits, cakes and stodgy puddings. The other culprit is caffeine, but if you currently have a lot of tea/ coffee/ fizzy drinks then you will need to cut down gradually in order to avoid withdrawal effects. Drink at least 1.5 litres of plain, still water daily but make sure you're not drinking anything 30 minutes either side of food.
Chew ALL your food really thoroughly - aim for 20 chews each mouthful. This is all incredibly helpful to your digestion, and once you are metabolising your fats properly your foggy feeling should lift. It also helps if you keeping your blood pressure stable by breathing slowly and deeply, and preferably doing a little stimulating exercise each day - anything between 10 and 30 minutes is ok, even if it's just running on the spot or doing some star jumps - anything to get your circulation going.
If you have very heavy periods then you need to take a good natural iron tonic such as Feroglobin.