Many thanks to everyone who responded so quickly. I called the Animal Poison hotline and they told me to watch him carefuly for 1-3 hours. I also did some looking on the internet and so far from what I can tell he is fine. I am not going out tonight, I'm just going to stay here with him to make sure he is fine. He is totally playful, respondes quickly to things, so I'm thinking that maybe he didn't eat one. The good thing is that the Emergency Vet is literally three minutes away.
While looking on the internet, I learned that some dogs are purposely given paxil for anxiety. Anyways, for a dog the size of Thor a 20mg would surely do bad things to him. Through all this panic I weighed him to compare his weight with the mg's that he took and Thor is a wopping 12lbs!
So I will keep you guys updated, I have calmed down...out of panic-mode. I just wanted to let you know that as for now I think it's going to be okay, and that he is acting normal.
Thanks so much for the support. I means so much that I know I can fall back on YT for support and great friends and great info. The first thing I thought of was "I have to check with YT!" So again, I really appreciate it.