First and foremost, make sure you have enough fibre in your diet. If you don't usually have wholegrain-type cereals, change to those. Whatever it is, it would be wise to see your chemist (probably no need to see your doctor just yet, since it's only been a few days) and see what s/he has to offer you in the way of laxatives or gastrointestinal stimulators to clear out your system. You may just have a bug or something that's causing bloatedness et cetera, and laxatives might help get things moving smoothly again. If it continues, see your doctor, but every now and again we get things like this that last a few days.