You sound like any number of us when we first got here.
Have you tried flying from BWI (a Southwest city) to a city SW flies to? Sometimes UA matches fares.
Recently some folks flew LGA/IAD/BUF. Maybe some other crazy routing is out there that can help you.
Here's what I did a long time ago:
After everyone went to sleep, I sat at the computer and kept plugging in city pairs.
Airport codes are available online (just make a hard copy).
Eventually you'll come up with something good. I know.