Yep, happened to me in the 80's and that was the end of weed for me. Simply not worth the risk of a repeat performance. Up unitl that point, weed was utterly relaxing and a wonderful experience, every single time. Then - bammo.
It's a panic attack to almost a psychedelic degree, plus and intense feeling of death. None of my friends ever experienced it, but I've read about it on the Net among others.
In India, weed is used as a spiritual drug. It's smoked by yogis - not haha winkwink yeahdude I'm a yogi - but real yogis. And it's acknowledged as dangerous because it can make you slip off the spiritual path into lassitude and indifference, and you can completely lose your spiritual spark. So it's not like it would make you physically sick - it's different than that. And a ot of studies in the West show that that kind of emotional effect is very common.
But in India, it's used to break through levels of ego that are protected by tension and anxiety. By staying anxious at a certain deep level, staying always "alert," certain deep emotions - especially sadness - can stay blocked and denied. Weed, at the right time in a spiritual practice, relaxes that tension, and releases the sadness underneath that anxiety lock. And the amount of sadness can be a lot!
Now, in yoga, when this is done, spiritual practices and meditations are used to process that sadness, to work through it, to witness it and to let its stuck energy flow again, and rebalance the psyche so that the yogi can proceed deeper. At that point, the weed is stopped because it is no longer necessary.
In the West, these things are not understood. Shrinks will provide you pills for panic attacks, but have zero understanding of the process. Pro-weed people will be pissed that you had a negative experience at all, because it threatens to expose them to doubt about the drug they are emotionally addicted to (and addicted because if they stop, their anxieties arise). Weed is all about sadness. It can release anxiety blocks and expose hidden sadness, or it can give a feeling of relaxation and peace and soothe anxiety and make one indifferent enough to deny their sadness.
So yeah, you had a real experience. And depending on what got released, it can be very scary. just remember one thing about it thoough - it's all an emotional memory. You already survived it. What's coming up is just the leftover energy from sad experiences, and it will not kill you. It's enegry overload, like waves sloshing back and forth until they settle down, because they've been blocked up and suddenly released.
So if you need anti-anxiety pills, take them minimally. STAY AWAY from antidepressants! They will destroy you completely! Work with the energy, exercise, be gentle with yourself, and it will slowly pass and reveal a deeper and stronger you. You're okay - really, you're okay. This os one of the best things that ever happened to you. You just have to ride it out.
P.S. Once you've processed the sadness and anxiety, weed won't be a problem anymore if you still want to smkoe it. But you won't want it like you used to, because the underlying drive to suppress the sadness won't be there - because the sadnesswon't be there.
Oh, and tobacco suppresses anger, and alcohol suppresses fear. Just saying. Think about it, tho.