Question about running--advice please

Ok, I had RNY spring of 09, lost half my weight, now at 128.  Last summer I started to do the c25k program, in October did a full 5k, 2 more in November.  Worked out in a gym all winter, hated the treadmill but loved the eliptical.  Have done 3 5k's already this spring and want to work toward a 10K in October.  I have a limited hill route that I'm working on to get further distance and am up to 4 miles.  When I want to do hills, I have a half mile up and about 1/3 down with another 1/2 mile of flat I do as a single circuit then I do it twice for about 2 3/4 miles. 

Here's my question.  Since I started with the hills, I am noticing that uphill isn't bad on my stide (although it is definately tougher), but down hill really seems to hurt.  I've also noticed that my foot strike is further back on my foot.  I was told I had a good stike earlier, but lately I'm worried that it's going to cause pain and maybe even injury. 

Does anyone have hints to help me with the foot strike and down hills?

Thanks for your help

One thing that I do is run down only using the knee joint. I try not to use my hips at all. It would be like tying a rope around your legs above the knee and running down. Not sure if it will help you but it has helped me. Also, if you are doing hill repeats, I'd walk down the hill.

Downhills are definitely harder on the quads.  Try to keep your hips under you and your form solid on the downhill side and you should be fine.

Keep up the good work!!

Darrell