Why do I feel like this every time I think about it.?

A few weeks ago, I did weed for the first time, and I tripped pretty bad. I was fine for about 20 minutes until I sat on my friends computer. My heart started beating harder and I sort of felt like I was going to die, but I knew that it was just a panic attack and that I'll be fine and I managed to calm down. Everything went smooth from there. Well my friend asked me to smoke with him again, and every time the thought of smoking with him comes up, my heart starts beating harder, and I get scared, so I took the liberty to brush up on the long-term effects of Marijuana and google'd it. I came upon this thread about this guy who smoked weed laced with cocaine and hes been having anxiety attacks. Do you think my weed could've been laced with coke? It's only when I think about smoking with him that I start getting scared. Am I always going to have panic attacks every time I smoke? Am I just trippin' right now and It's all my head? Someone please calm me down lol.Don't tell me to stop please, just answer my questions.