Hey.
You seem to divide the world into two parts: People and things that are stupid or potentially harmful, and people and things that are not stupid or that are beneficial to you. The result seems to be that you automatically rebel against that which and whom you designate as "stupid." This makes sense to me, given your history. But this leaves you basing your decisions primarily on what feels good, rather than what might be of most benefit for you. (You get nothing from therapy, and you're afraid of antidepressants.) That's a deep hole that takes some work to climb out of.
THC, a chemical through and through, is the active ingredient in cannabis. If it didn't effect attractive brain changes for you, you wouldn't be using it. Yet you dismiss it out of hand as not being a chemical because it tends to make you feel better. Deciding that someone or something has value based exclusively or primarily on what they make us feel is a large part of how we addicts and alcoholics engage the world. Or attempt to avoid engaging the world.
Many things can happen when we ingest substances of abuse. Very often, our mood, state of mind or state of being is magnified in ways that are only partly predictable. For example, smoking seems to settle you to a certain extent, but it also induces paranoia, an artifact of depression. It also seems to help you to feel more competent and to be more productive. All of this seems to melt away when you're not smoking. This dynamic is referred to as "psychological dependence." You may even believe that you need to smoke in order to do well at work.
I can't make out clearly where you're at currently, but it seems that you complied with your GF's request to stop smoking, at least for a time -- she must have seen something in you that scared her -- and then you went back to drinking. Smoking weed may have made it easier for you to stop drinking, but you clearly still have a problem with alcohol. Perhaps now you're doing both?
The thing is that, both alcohol and weed make depression and depressive symptoms worse. That you experience little or no pleasure in most of your activities, the few that remain, suggests that this is happening with you. As it seems in your case (based on your GF's observations), you need to smoke a great deal in order to get the desired effect, so your tolerance is also great.
At the end of your OP, you asked, "How do you guys see it? "
What you describe as depression and low self-esteem will only get worse with drinking. Though you may find mixed reports around the effects of cannabis relative to self-esteem, the consensus is that, though smoking weed may reveal aspects of one's self-regard, it cannot repair it and typically makes things worse over time.
Other than all that, it seems that you're currently living a life without much joy, that you have little to look forward to, and that you believe that if you were to stop both drinking and smoking that you would somehow be annihilated by the memories of your past. Many people who learn to live a better life with the help of therapy only do so after one or more "false starts" in therapy. If "feeling better" is your goal, than you're likely to be disappointed. And if all you're doing in therapy is either biding time or having "fun," then something's wrong. As is true of sobriety, there are things in therapy that are painful and disturbing, sometimes significantly so, and it's the commitment to work through all of that which can bring us to a better place.