I noticed there is a lot of frozen condensation on the inside of my windows. It is -5° F outside right now. Should i be worried?
While this might not be a huge problem on its own, it has some negative side effects. Your windows are letting a lot of cold in through the pane and around the edges. This significantly increases heating costs and it can add uncomfortable drafts. If that frost melts and runs into the wood, it can cause mold which potentially could turn into a big problem.
If I were in your shoes, I would seriously consider upgrading my windows and if -5°F is common (or even if 15°F were common) then it may be worthwhile to look into some high quality 3 pane windows. When looking at windows, Argon filled is a plus but ultimately you mostly want to look at the U-factor. You want to get windows with as low of a U-factor as possible.