The only time this has ever happened to me, was when I smoked a dutch tulip, alone. Weed-tobacco ratio was about 80-20 (I like the headrush from the tobaccy sometimes). By the end of the tulip, I was on my back, feeling my heart race, wondering if I'd possibly done something I would regret. Five minutes later, bending over the toilet, I was regretting it. After about 10 minutes, though, I was pretty much alright (if ridiculously stoned . . .which is alright

).
Granted, I had tobacco, which can make you nauseous if you smoke too much/too fast, the same thing can happen with large amounts of weed, even to veteran stoners. The best thing to do is simply lay down, and let yourself relax. Don't think about it, just lay down and wait for your body and mind calm down, just like you would for a bad shroom or cid trip. Weed is, after all, a mild psychedelic.
I'd suggest smoking a small amount of that bud, and try not to have any predispositions about it. See how it feels. I highly doubt anyone would lace your weed with meth, though it is possible. If it gives you the same feeling, whether this is due to placebo or not, I'd recommend throwing it out. If a certain weed makes you panicky, there's no point in keeping it.