A third voice: if there's blood and mucus in your stools, go and see a doctor ASAP to get yourself looked at to rule out Crohn's/colitis, as these are conditions that can occur in young people. You should still see a doctor as soon as you can to make sure you don't have Coeliac disease, etc.
I have IBS as a result of having Ehlers-Danlos Syndrome so I can give you some advice in the meantime. I would strongly recommend keeping a food and symptom diary and pay close attention to it to work out if there's anything that makes your symptoms worse. You should also take the time to eat your food slowly- give yourself plenty of time to eat and do not rush. Similarly, don't leave long gaps between meals as this will irritate your symptoms further. Buscopan is a good thing to try (obviously read the label), and my doctor put me on Colofac when I was hardly eating as a result of the IBS last year, it worked wonders. Try drinking peppermint tea- it soothes your digestive system. If you're nauseous, I highly recommend ginger tea, too. Have plenty to drink, don't let yourself get dehydrated. If you find that stress is making your symptoms flare, make time every day to relax and unwind, whatever that may be. Get plenty of rest, too, as being overtired can worsen symptoms.
Good luck, and if you have any questions, don't be afraid to ask!