But to reiterate what I said in that post, it's very normal to feel depressed after stopping. For me, and for others, we used weed to put off dealing with stress, and life. I did it for 5 years, so when I stopped, that buffer between my problems and myself was removed, and I had to learn to engage with all the minor things I put off.
Like you, I had a panic attack from smoking too much, which also helped direct me toward stopping, it can be a good wake up call.
That creeping emptiness and hopelessness will fade, I recommend meditation. I use meditation to honestly engage with issues that bother me. I watched an amazing ted talk on emotional first aid, It's really great, you should watch it when you have 20 minutes. My take away from it, is that from a young age, we're taught to take physical damage to ourselves seriously, but we're not taught to take emotional injuries nearly as seriously. And for me, and perhaps for you, smoking weed helped you cover up emotional injuries you sustained over a period of time. So the goal then, is to address those by first acknowledging that they exist, figuring out what they are specifically, and then creating a plan to work on those issues. It's a lot of work, but it gets better in time, much more so if you address these things. I'm on day 117, just a few days shy of 4 months, and I truly believe that focusing on my emotional injuries, both big and small, as well as meditating to help create a balance in my mind have been incredibly helpful in my quitting.
I hope this helps you, that depression sucks, but there's always a reason, and finding that reason will help you feel better.