I completed C25K 7 months ago. I can run three miles (not easy but I can do it) the first problem is I am really slow. I run on a treadmill (I know not ideal) 4 miles an hour. I do have it inclined also. I would like to increase my pace but not sure the best way to do it? If I try and do 5 miles an hour I am out of breath after a short time. Anyone have some advice on how best to do this?
Also my next problem - sorry in advance! I have stomach issues when I run (which is why I stick to the treadmill) sometimes it can get really bad and I will ahve to get off the treadmill a few times to go to the bathroom. I don't know what to do to fix this. It is very aggravating! I want to be able to run and enjoy it instead of dreading it every time. Sometimes I can not complete the three miles running I will have to walk it. I can walk at the same pace and it doesn't bother me.
Keep your current 15:00 per mile pace as it is a very good pace for beginning runners.
As you progress, DO NOT go faster, go further instead.
A good rule of thumb for a beginner to adhere to is to add distance on a percentage basis. If you're able to run say 3 miles now, work your way up to say 3.3 miles (a 10% bump), and then once you stabilize at 3.3 miles, bump it up another 10%.
Once you're able to run 6 miles fairly consistently, then, and only then, should you start thinking about speeding things up a bit.
As for your GI issues, I have found bananas help in this regard; others keep pushing forward until their body gets used to the extra activity. Keep running long enough, even if initially on a treadmill, and you're body will adapt.
I like the advice that Shipo gave. I would add that if you are going to speed up the treadmill instead of jumping from 4 to 5 mph try just going up .25 at a time and give yourself time to get use to it.