Sensitive to marijuana but wasn't before?

I just can't find any explanation around as to why all of a sudden I'm sensitive to the hit of the weed. I started to smoke weed when I was around 14 (couple times a month), I could have about 4 cones until I felt relaxed.

I was 17 when I decided I would stop. Now 20. Last year I went out to a party, everyone around the fire &we had some really nice stuff. Everyone had finished their joint & I had just lit mine, I finished my joint just like everybody else but they were all relaxed. It effected me a lot. I had muscle spasms/involuntary twitches, I kept telling everybody there were "Bugs under my skin", it just felt how you would pinch yourself, but that all over my body.

I was in & out of it. People were talking or trying to talk to me but I just wasn't there. I was extremely paranoid.

Everyone else was giggly & happy.

My friends told me everything about the night the next day. Something else being that I was too scared to go to the toilet because of tarantulas. I had everyone 'check' the house for 'a man with a knife' & was unable to sleep on my own because of these paranoid thoughts.

I didn't touch weed that day on until about a week ago, where I thought maybe I'll try it through a bong, but the tiniest piece. Seriously, it was the most ridiculous smallest cone ever, I took that & sat there & all the symptoms fired up. Twitches/spasms/pinches/paranoid.

It was never like this before. Why now? It's scary stuff. I can't understand why. I use to love smoking the stuff.