Hey Runnerklm,
I want to encourage you to continue in establishing the active life style as just that, a Lifestyle Choice". I encourage you to hang on long enough that you can get past all of the beginning stuff you get to a point where you can really feel the difference that the lifestyle will give you in emotion, physical, spiritual and self actualization. Go slow, don't over do it, but keep it up.
There are many activities that you can do to be active. My favorite is running even after knee surgeries and all. It is my favorite high.
The change of activity could really be the major cause of the knee pain. Don't run on concrete. This is a killer. Asphalt is much better. Smooth dirt or trail is best. Running, walking is great. Just get out and get it done.
Can I also suggest that you document what you are doing. Log in what ever it is so that you have a record to see the progress that you WILL make.
Good suggestions by the other reply. (I don't remember her name) But you don't really want to rely on too much medication. If you are heavy and putting lots of force on your body mix the run and walk well. You should see unwanted pounds fall off very quickly by getting off the couch. You diet is important too, but just giving your body a regular change of respiratory and heart rate you should see soon that you will sleep better, be more regular in the restroom, and feel better toward life in general.
Good luck and keep it up. Let us know your struggles and successes so that we can inspire and celebrate.
Paul828