ChrisO --
It has been a week since you started this thread. How are you doing? Here's my two cents:
You do not quantify what "a lot" of drinking is, but if you're drinking a handful of beers in the evening hours only, you are likely able to quit without feeling withdrawal effects. Classic (or "Hollywood," if you will) withdrawal symptoms include the shakes and even delirium, but the symptoms can be more insidious, as I have personally found, and can include anxiety, inability to concentrate, and a profound sense of a lack of well being. Hopefully you are aware that alcohol withdrawal is one of the most serious types of withdrawal in terms of your health, so if you have *any* serious concerns that you are experiencing acute alcohol withdrawal, seek medical help immediately. On the other hand, in the more likely event that you are not physically dependent on alcohol, I would recommend going off the stuff entirely for maybe a month or a few and then re-assess your relationship with drinking. Perhaps you are the type who can have a few drinks on the occasional social venture and then let it stop there. But if two or three drinks leaves you craving more, that could signal a problem. And while many people do drink daily (as I have in the past), it is simply not something to recommend to anyone who has had doubts about how doing so has impacted their physical and mental health and their relationships or job performance.
So far as the pot, I have to take issue with our fellow board meraber, coloradopablo, regarding withdrawal. My wife, like you, takes Zoloft and has smoked regularly in the past, and has as well cold-turkey'd it on a couple of occasions, and believe me, she suffered more than some insomnia. In both instances, her depression symptoms (which include severe anxiety) resurfaced despite the Zoloft. Although this type of withdrawal isn't physically dangerous, the last instance led me to insist that she see a doctor, from whom she was fortunate enough to receive a short-term supply of a benzodiazepine. It took maybe ten days, but with the help of the tranquilizer, she was able to get back on her feet. Not that I'm saying this would be the case for you -- yes, many can stop pot with little to no withdrawal symptoms -- but it's something to keep in mind while you're on an SSRI.
Kudos to you for facing head-on how daily drug use is negatively affecting you (for too many, denial is the easier route), and all the best as you work to take charge of your life.