I think you should feel free to repeat W3 as many time as you want before moving on.  Also maybe look at the schedule and write yourself a week or two thta splits the differrence between W3 and 4  and do that before moving on.  Nothing says you have to do the whole program in 9 weeks and you are not going to just do 9 weeks and quit, you are beginning to change your life!  

I am just finishing W9 and I haven't exercised in 35 years, so I understand your struggle.  I can't just go out an exercise for the "thrill" of it, I had to have a motivation, so I picked a 5K that was far enough in the future to fit the schedule and paid for the entry fee....that kept me motivated.     Do you think that might help?   Also, nothing says you have to run the whole 5K, if you register....jog as much as you can and then walk....the goal the first time is completion and the solid satisfaction that you did it.

I am impressed that you are trying again.  YOU CAN DO IT!

Also, I kep myself accountable by loggin in here every run day and logging how I felt, what the weather was like, how I did etc....in a weird way that kept me going too.   Laura, what you are doing is great and you are giving yourself one of the best gifts you could possibly ever give.  Rock on, Baby!

Did you actually try to run the longer run?  I was really unsure about the increase before I did it, but when the day came to actually run it, I found out I could do it.  It's a huge confidence booster.  One thing I did though was run a bit longer on the earlier runs - splitting the difference - so the jump wasn't quite as extreme.  As long as you keep a slow easy pace, it is doable.  The problem is usually more a head problem than a physical problem.  I think that by asking for such a big jump, the program teaches you that you are capable of doing more than you thought you were, which helps a lot when you get to the point of running nonstop.