To run...or not to run

I have been a little lazy with adding the jogs intervals in my lunchtime walk...

I think a part of the problem is that I am just too scared to pick up the pace again. 

To take you back, I started the daily work walks in January and was pushing to walk at a good pace.  I quickly found that by increasing my stride I developed some really painful shin splints and was pretty much out of commission with cramps so bad I was not able to finish what is now a pretty easy 3 mile walk.

I have been working on modifying my stride, bought new shoes to add some extra cushion and took it easy to allow myself to heal.  I do not like to take it easy!

I am now back to walking at a brisk pace and started to add a few minutes of jogging to the routine.  In less than a minute my knees start to ache and I pull back to walk a bit more.  It seems like each time I try the fear of my body failing me holds me back.

I have been reading several blogs lately and the success stories are inspiring.  I know they all say just suck it up and do it and you will be amazed with the results.  How do you get past this???

I desperately want to see if I can really be a "runner".  I mean more then the sprints that I used to pull off in high school.  I want it all.  Yeah - no paience here!  Then I think what happens if I blow out me knee or pull my back again.  Then I would be out of commission for god knows how long...

Help!