I started running before C25k was invented. I was <9st and had been going to the gym for a year or so. I found running terribly hard to start with, it took many weeks to build up the stamina. I signed up for Race for Life and was determined to run it all, I can remember struggling to do even 4k on the treadmill and feeling like I was going to die and I'd been running for a few months by then!
Now, I'm more than 10 years older, about the same weight, can run 10k non-stop with ease and I STILL find 3-4k the moment when I most want to stop!
Don't give up, take as long as you need but you CAN do this.
I started the C25K recently, I have just finished week 3. I am still finding it really really hard, I get out of breath so easy. I did the shred before starting the C25K so had built up some fitness, I can't understand why I am finding it so difficult. Any ideas?