Glasses to contact lenses.?

I recently got my 1st pair of contact lenses but when I put them in my eyes were really blurry. I had them in for like 30minutes and nothing changed and I can see better without them. I told my optician and she ordered new ones but they're the same and I wore them for longer. I had them in at school and they were so bad that I couldn't see what the teacher was writing on the board. Does this normally happen or is the prescription wrong? I'm long sighted if that helps.