Hi
4 months isnt long to train, if you havent done a massive amount of running before.
You need to push yourself and try and run further i was doing it like this:-
Sunday - Long run 8-12 miles
Monday - Off
Tuesday Short run 3 miles
Wednesday - Medium Run 5-7 miles
Thursday - Short run 3 miles
Friday - Off
Saturday - Short run 3 miles
You need to go on a run and push yourself even if you cant run, walk fast, you need to practice just being on your feet. As you're gonna be on your feet for 2 hours. Shoes, diet and hydration are very important as well dont forget these. Get yourself a foam roller as well, will help massively with recovery.
If you can only just manage 1 milers try upping the distance on 1 or 2 of your runs. It will get easier but you have to put the miles in. Try and up it every week even if its by more minutes running rather than complete miles.
I also use
http://www.endomondo.com that way i can see how far and fast i have run. (GPS tracking for your mobile phone)
Good luck :-)