Felt nauseous after taking Dramamine?

I took half a Dramamine and when I swallowed with water, it got stuck at the back of my throat. I swallowed again and I felt really nauseous, like when your head feels like your hallucinating. I'm really scared cause I don't know if Dramamine expires or not. I'm sure it was at least three or two years old. Help! I'm so scared I'm shivering.