I've created music in my head..?

www.finale.com - ten bucks - get Finale Notepad. Yes, you will have to clink in the notes. If you can afford a better version ( not the top program, FINALE!!!) then you can connect a keyboard and play in your ear-worm. You can also sing this to someone who have musical abilities and software, and THEY can notate it for you - and teach you how to take it from there.