Hi Michael
Poor you, but welcome to the most helpful forum on this illness. We have all been through what you are experiencing. Stephanie has said most of the things I would say. But please be reassured that you will feel better and learn to cope with the illness and live a normal life. I have lived with this for 15 years, and worked full time for 10 of them (I'm retired now). I also played table tennis to a high standard during this time as well. You do need to be prepared to experience discomfort for several weeks, or possibly more until the infection and inflammation die down, but they will.
There are things you can do to help yourself. As Stephanie says, first thing is to see a doctor and have the tests. That's usually a colonoscopy and/or CT scan. The colonoscopy is not pleasant but the prep will certainly clear out your system. Several people have posted their experiences. The CT scan is much easier.
Then there are things which will help your bowels. There is a product called psyllium husk which comes in a powder form (one generic name is Fybogel). It is orange flavoured, you mix it with water and take once or twice a day. I get mine on prescription from my GP, or you can buy over the counter (whichever is most cost effective for you). It bulks up and softens stools, which once you get over the acute stage, you will find really helps to regulate you. Many people on this forum recommend it.
My dietary experiences differ slightly from Stephanie, but as she says, everyone is different. I was advised to go gluten free, high fibre and low fat, so that is the diet I follow, with lots of fresh fruit, vegetables and liquids. However the bland diet Stephanie described is the one recommended to reduce the work the bowel has to do, so ideal for you in your current stage or in future attacks. Many people also recommend pure Aloe Vera juice and probiotic yogurt drinks. I found aloe vera reduced my pain to twinges within 5 days of starting it. It's bitter but it only lasts a few seconds.
Most young men your age will enjoy time out with their mates, so you might need to monitor what sort of things affect you. Nuts and seeds are a well known trigger, as are high fat foods. If you like takeaways, you might need to become fairly selective, but you'll soon find out your triggers. Exercise and weight control are also important, so small portions are a good idea, until you learn what your system is happy with.
This will take you time to come to terms with but I'm sure as you feel better you will feel more positive. I spent a lot of time going through all the posts on this website and it is full of helpful tips and information. Best wishes.