Lakeshore Home Diagnostics can help.
We use blower door testing in conjunction with an infrared camera and a smoke pencil to determine areas of air leakage. Once the leaks have been identified we can assist you in your efforts in sealing the leaks. In many cases the solutions are inexpensive and may include things like caulking around doors and windows, sealing penetrations through the rim joist or adding closed cell foam weather stripping around an attic or crawlspace hatch.
There is no reason for you to be cold in your own home!