Most likely you over reacted. The numbness is a strange though. It is common for your body to feel parallized at times when you are high though depending on what type you smoke.

It is a rare occurence but sometimes people do get laced weed. A friend in HS smoked some at a concert and went blind for a few hours. That was some scary shit, not sure what was in that.

I wouldn't be to worried about it though, the mind can play serious tricks on you. The first time I ate weed I felt like I was going to die at one point. I had to keep reminding myself it was only cannabis and everything was going to be ok. The fact you only smoke a few times a month makes me think you just got really good bud and got scared because the high was stronger than expected.

Sorry I can't be of more help. But you seem to be in the clear, so no major damage done.