Mary:
How has it been going? Any update?
Worried that a week off will put you in danger of stopping altogether? It ain't gonna happen - not after what you said you've done through the years to get your runs in. I have a somewhat similar story. I've run at 4:00AM because that was the only time of day I could do it. I've run when it's -10 deg F. I've run in small circles because the compound where I was staying for a business trip was the only safe place I could go. I've been battling foot issues for 2 *years* and I still think of myself as a runner who is sidelined temporarily. It's not that I haven't been able to run at all - but my previous and now desired mileage of 25 mpw just hasn't been happening. This past summer I was up to 12 mpw - but then the wheels came off after I went on a backpacking trip. I haven't run at all since August.
As you hopefully have now experienced you're not going to lose fitness in a week. Having pain after a week off and starting to use phrases like "....maybe my running days are over." - well - we're not going to LET you out of the running community that easily.
Basically you've got some work to do. Work to figure out what is going on with the knee. You said you're underemployed and have little (no?) benefits, however knees are NOT something to mess around with. I would definitely NOT run through the pain - especially if you're experiencing catching. All these resources (forums, Google, etc.) can help a lot in having an amateur (like you and me) figure out what is going on. I'm not talking self-medicine, but rather fairly aggressive amateur research and reading about knee issues, what they are, how they're treated, prognosis, etc. There is a user on the runnersworld.com Injuries forum (mmrocker13) who knows a TON about knees. You might look for some of her posts and/or PM her.
Hang in there. I hope things have improved.
Jim