How dose one know if one has a liver problem?

Easily. Liver disease is likely present if the blood transaminases &/or liver alkaline phophatase ("liver function tests") are up, or the liver is painful, or conjugated or mixed jaundice is present. Advanced liver disease may instead have fluid in the belly, massive vomiting, and grave systemic illness but these will be obvious. Charlatans diagnose "liver disease" when it's not present. Be careful.