Hiya Anne, just to reassure you schizophrenia is actually not very common - it affects just about 1% of the population. I don't suppose an online test gives much in the way of real indicators anyway, more just worrying for you. One major problem of psychosis is losing touch with what's around you and it sounds like you have your feet pretty firmly planted. I'm sure people you know would notice anyway if there was a problem with that.
One word that comes to mind when I read your post is 'balance'. Just maybe trying to enjoy your creativity but develop some social practical activities as well, if you feel up to it. Was the song looping a one off? I've had something similar before now but I just assumed it was because of liking the song. Or do you get other 'stuck' thoughts? Just wondered.