Hi Becky! Just get out and DO IT

Other replies give good advice for working on technique, but for now, you're absolutely right about DNS being worse than not trying at all. Not only worse, but not FUN!

When you find your way to a pool, start nice and easy. It's ok to swim a length, or two, or what ever you can do comfortably, take 10 or 20 or 40 or 60 seconds rest, then do that distance again, rest .... and so on. After just a few sessions, you'll find that you are swimming longer and resting less. If you know how to do different strokes, then mix it up a bit to keep from being bored. You'll be building fitness and confidence while following up on technique advice from the other posts.

Have fun & let us know how the swimming goes!