Congratulations, Aine for discovering the method. This is how I compose music, exactly as you have it, by messing around, and coming up with interesting or exciting chord progressions before the melody. I can say that I pretty much have NEVER come up with a melody first, and then put chords and lyrics around it. I don't seem to be wired that way.

How do I create a melody? Well, I suppose it has a lot to do with improvisation. Maybe it's easier for me, because I write, or use other's, lyrics first, then ascribe a chord progression I have come up with, to the lyrics. It's then just a matter of playing the chords, and just singing the words with an improvised melody. Sometimes you can work for hours before you pump out anything that sounds good. Other times it's like magic, the lyrics, combined with the chord prog form an immediate melody in your head.

Some times I work from lyrics alone, with no chords in mind, and just try to come up with chord progs on the spot. I usually work it taking one lyrical phrase at a time. Be sure to have a tape recorder handy, because when I come with a satisfactory little melody for the particular phrase, I record it immediately so I don't forget it. Then I move on the the next one, whilst going back the the first phrase, and memorizing it a bit, so I can make a smooth transfer from one phrase to another. Hopefully in the end you can come up with something very catchy & beautiful. Good luck!

--Matt