Does drinking every night constitute abuse?

Unmanageability. If it is causing problems for you or your family or friends, you might consider attending a meeting of alcoholics anonymous.
Not necessarily. Depending on whether the drug or alcohol use causes problems. If it causes problems, either health or social, then it is abuse. There are people who drink daily and don't have any bad consequences. There are also people who drink only on the weekends and have severe bad consequences. Drinking per se is not the issue. It is drinking too much, and at the wrong time, that causes problems.