Hello Pdorez: I see this is your first post here on PC. So... welcome to PsychCentral… from the Skeezyks!

I hope you find the time you spend here to be of benefit.
I have a few comments with regard to your post. I'm an older person.

And my spouse & I have been married for over 30 years. My experience has been that long-term relationships change over time. The "romance", as it were, gradually drains away. Under the best of circumstances, it leaves something like an endearing (more platonic) love & respect for one another. (In other less ideal cases, it simply becomes a matter of inertia.)

But, in any case, my experience suggests to me that romantic relationships change over time. They necessarily cool. That's just the way it is. And, as a result the two people in the relationship must find new ways to relate to one another if they are to remain a couple.

So what you have to decide is if your relationship with your gf has cooled to the extent that you can no longer continue to be a part of it. But keep in mind that the next relationship, & the next after that, aren't going to turn out differently in the end.
It may be that the problem primarily lies within yourself... you feel unfulfilled within yourself (hence the self-medicating & drinking) & so you feel unfulfilled within your relationship with your gf & want to look elsewhere. However, since it is your own lack of inner fulfillment that is driving this urge, your next relationship likely won't turn out any differently because you'll still be carrying your basic lack of inner fulfillment into that next relationship... & the one after that. In effect, you're chasing a chimera... seeking inner fulfillment in external relationships.
I took Cymbalta for a couple of years, I guess it was. From my perspective, continuing to drink while you're taking psych med's is really just asking for trouble. It's difficult enough to find an effective med to begin with along with the appropriate dosage, & to maintain this over time, without adding in the effects of alcohol on top of it. From my perspective, continuing to drink while you're on psych med's is like taking medication for a disease & then also taking something to nullify the therapeutic effects of the medication. Why would one do that?
One other thing I will mention, with regard to Cymbalta, is that when I was taking it, I found I was able to talk about things I don't believe I would never have mentioned had I not been on the med.

I guess you might say it "loosened my lips".

This can be either a good thing or a bad thing depending on the situation, I suppose. In my case, I regret that it happened. But, either way, I wasn't surprised by your comment regarding your "torrent of negative comments and ideas."
PsychCentral is a great place to get information as well as support for mental health issues. There are many knowledgeable & caring members here. The more you post, & reply to other members’ posts, the more a part of the community you will become. Plus there are social groups you can join & chat rooms where you’ll be able to connect with other PC members in real time (once your first 5 posts have been reviewed & approved.) Lots of great stuff! So please keep posting!