travel related Problems pain and diarrhoea

First off, some info, I am male 16 years old and live in Canada. I was away on vacation to Jamaica for 1 week and felt fine the whole time but now that I've come back I have been experiencing a few bad symptoms. The worst one is that every 20-25 minutes I get about 10 minutes of intense pressure on my lower stomach area which to me feels kinda like gas pains. It goes away and comes in waves, sometimes it is okay but other times it is almost unbearable where I clench my teeth amazingly hard. At first it was accompanied by regular bowel movements but now about 50% of the time I receive the pain I also get diarrhoea. Also at the beginning I was having some incredibly smelly farts that almost had a burning stench but those appear to have subsided. The worst part is that now I'm getting blood in with it, so I went to the doctor to make sure I got it fixed. Unfortunately, they didn't do much at all for me other than that he told me it was a haemorrhoidal bacteria. He said that it has to go away on its own but he checked my blood to make sure it wasn't affecting anything else but the blood-work came back fine. However it doesn't seem to be going away and the pain is just as bad, if anyone can help with what I should take or what it could be that would be great, thanks.