technically your liver is self healing, but since having DD and HELLP syndrome when DD was born mine have been out of kilter too. Mine were monitored constantly throughout my last 2 pregs and didn't seem to change much until right at the end.
Like you I'm not a drinker (and now even more so) no pill popping, drugs, tattoos. I try to keep a good clean dies these days and have bouts where I know they're a bit average, but the doctors have told me that some people are just like that
I've had all the scans/tests and they can't find anything.