Im a 19yr old male, recently I went to mexico, about the 3rd day I was there I had daiareah, and thought it was because I was dehydrated,I haven't had diareah since. Since then I had a mucus subsatance on my stool, with a tiny bit of red stuff, I get adomomin pain right before I go to the bathroom, then when I go to the bathroom, only a bit of stool comes out,when it feels like a lot more should have came out. And I feel fine afterwards.

Ever since the 60's I have always heard that diarrhea from visiting Mexico was normal.
They always said 'Don't drink the water when you go to Mexico'. If it keeps up you should probably check with the doctor.
Here is a search engine you can check more on it
diarrhea from visiting mexico - Google Search

I think from what you are saying,you have passed a tiny bit of blood in your stools. Tell your doc about this,so he has it on file and if this keeps happening(feeling of not emptying bowel),tell your doc to refer you to a gastroentologist (digestive system doc) at hospital,for a colonoscopy as you may have an underlying condition,as the main symptom you say you had are from an illness called IBD.(inflammatory bowel disease)