Anal Leakage, Possible Hemorrhoids

Hello, the first thing I would like to say is thanks for reading my post. I'm freaking out right now and I believe I have just encountered my first anal leakage and I'm only 17. The story is my girlfriend and I were just doing our normal business in our home, then out of no where we started smelling this horrible stench. I assumed it was my dog because he had just come in from outside and was laying on my bed next to us. But I smelt him over and over to see if he was what was causing it, I finally decided that it was not him. So I started thinking if maybe it was me because ever since January 2011, I have been having problems with my rectum starting with constipation and painful bowel movements.

I got checked out by my doctor and she said that I just need more fiber in my diet. So I changed my diet and soon the constipation was over. Then a few months later I had another painful bowel movement so I decided to examine my anus with a mirror. I noticed a purple-ish bump and it scared me. I figured it was a hemorrhoid but I just tried to ignore it because I was too afraid to see the doctor about it. The pain eventually went away and it didn't come back for awhile because football season came and I was doing lots of exercises and drinking lots of water so I think that helped.

Then winter came and my daily exercises stopped because I don't like going out in the cold (I live in Ohio) and I'm a big computer geek so I'm on my butt a lot. I also changed my diet to consuming lots of fast food and snacks and drinking lots of pop with little to no water at all. Now I get stomach pains, itching near my anus and I have very few bowel movements a week.

And now were back to the anal leakage, I went to the bathroom and smelt my boxers and they had the foul odor on it. So I examined my anus again and noticed there was some kind of liquid around it. I jumped in the shower and cleaned it up, then I had a bowel movement. This was all about an hour ago and it all seems to be dry down there for now.

But I am scared because I don't want this to ruin my life, so please if you could help me I would be very thankful.

Sorry for making this into novel, I wanted to provide as much details as possible.