DW Runners

Hi, runners! *waves timidly*

I just started running...four weeks ago? because I discovered that running abates symptoms of my spouse-creature's mental illness, and so I'm running to keep him running (he's a long-time distance runner, high school cross country and track, etc., but has lost a lot of his running self-discipline).

I have worked from not being able to run 0.5 mi without taking a break to *almost* hitting 2 mi, which has been really exciting for me. I'm hoping to run a 5k in late March, as sort of a milestone for myself.

On the down side, I have noticed lately that running/exercise walking is causing me pain in the backs of my knees, in a line across the back and also somewhat down the muscle on the back inside. I am probably horribly wrong, but the feeling I'm getting makes me feel like I'm overextending/locking my knees at some point in my stride.

How do I fix this? Are there stretches for those muscles? Any advice on where to find out if I need to change my running stride (and how the h*ll to do that?)?

Thanks!