Not necessarily.
My drinking truly escalated after my partner-at-the-time engaged in an indiscretion with an ex-girlfriend. I was on my way down, for sure, but he wasn't the alcoholic, I was. Since he lied about this indiscretion for over a month before finally coming clean, and being that it happened a mere 3 days after we flew across the country in the name of his asking my mother and father for my hand in marriage, I guess we both felt really lost.
I think people who are checked out on or of anything can potentially compartmentalize and act out without considering the consequences. We can deny that there will be consequences, by sweeping whatever under the rug and living in the moment of, 'hey, I'll pretend it didn't happen, and I will believe the lie until it is the truth'. I know that alcohol really messed with my sexual behavior, and that's been on my mind a lot today.
Some people just don't see infidelity as a form of betrayal. I do. Having unknowingly been 'the other woman' more than once and turning into a mega-witch upon finding out, I've had to work on choosing partners who are emotionally, physically and mentally available to me.
Not all alcoholics are bad apples that lack character. A lot of us just don't know how to cope with pain, discomfort or a lack of reciprocity in relationships.
Heck, you don't even have to be an addict to engage in these behaviors. You might be an addict on another spectrum.
Take care of yourself, though. We're here for you.