I Have Been Sick For A Few Weeks With Congestion

I have been sick for a few weeks with congestion and stomach issues, figured it was just a virus. Prior to that I have been dealing a infected tooth two roundS of antibiotics, a root canal and a crown for three months. Today I was feeling better for a change until lunch time I was eating and watching TV and my vision went blurred I couldn't focus, I got nausea and shaky. What could be the problem.?