Becky, don't give up, it does get easier. The key is starting off really really slow. You might think that someone could pass you at a walk but that doesn't matter, so long as you are jogging at a speed that you consider running and one that isn't killing your lungs. Another thing is while you are getting use to it do some walking on the days that you don't do the program, it will also help you along.
I'm 30yrs old and I'm also 100+ pound overweight, 57kgs (now) to be exact. I had been walking for a while and lost a wee bit of weight doing that then I one night I wasn't able to do my usual walk as my pants kept falling down. I have horses so I stole a bit of baling twine to use as a belt and decided to go for a walk while the horses were eating. Next thing I know I'm jogging/walking. This first one I was probably only jogging for about 30 sec all up and walking two minutes. It was bloody torture! but I felt really good at the end thinking I had done it. Also the distance at the time seemed so long but its now far to short! I started doing the c25k program after that and I do have to repet the weeks to be able to progress.
Yesterday I decided to not do the actual program but just run as far as I could then walk just to see how far my running has come, I was able to do two lots of 3min 30 sec and a couple of 2min 30sec before calling it a day, didn't want to over do it. This is a huge mile stone for me. I have never been a runner, always a walker, last time I tried to take up running (about 5 years ago) I got serious shin splints, looking back now I was just doing too much and going too fast. I did start off this time getting splints but after doing some reading I discovered that I need to bring the speed back a bit, which worked for me. I needed to allow my body to strengthen and get used to it. If I think its about to get sore I just slow down a bit. I also imported some KT Tape (I live in New Zealand) for shin splints and it truely does work, for me at least.
I've lost 10kgs now (think that is 22 pounds) and I feel much better for it, still have a loooong way to go but I'm enjoying running now, not something I ever thought I'd say! If I can do it, believe me, you can aswell.