What Causes Head Spins After Surgery For Hernia?

I hope so, I had vertical hernia surgery march 31 a week later I popped a stitch and seen my surgeon who said everything was good, a week later I popped the deepest stitch that I had the next night I started having head spins, every time I lay down or get up or sit in a chair and lean back my head spins, can you please give me an answer, thank you.