My son will be turning 3 in a few days and his speech to me seems like it's going in reverse. He says some words that we can understand and then he will go into jibber-jabber. I have no idea why that is. His hearing was checked and that came back fine. We went to the specilaist and they said he did not need therepy. Now he is talking like this. Should I worry?

I would suggest talking to his doctor. Talking and then backsliding in speech at 2 or 3 is a key symptom of Autism.
Good luck hon. Hopefully it is something simple.