Constant bowel movements/diarrhea/stomach ahches

I'm 18 years old and every since I was younger I have always known that I was lactose intolerant. Every time I would eat even the smallest amount of a dairy product or something with dairy in it, I would immediately get a burning and cramping in my stomach and have to run to the bathroom right away. When I would go to the bathroom, the results varied from a normal looking bowel movement to diarrhea. I had been a vegetarian for the last year and a half, and recently have gone completely vegan. Although I've eliminated dairy completely from my diet, I am STILL have the exact same problem. I decided to go vegan for personal reasons, but I also thought it would be plus considering I was lactose intolerant and would help my stomach problems. Apparently, I must not be lactose intolerant because the problems are still occurring. Now, not only am I still having these constant stomach aches no matter what I eat, I have also started to feel a burning sensation in my intestine area WHILE going to the bathroom. It feels as if something WAY too big is trying to fit through and as if someone is pouring a cup of acid down my intestines. I've even gotten tear-eyed while on the toilet. I am going for my physical next week and decided to start a food journal to go over things with my doctor.

ANY suggestions of what may be going on with me would be greatly appreciated.
Thank you