Can a proposed plea agreement decision be reversed?

My case had been set to trial and that date and judge were rescheduled and public defender replaced due to a new position somewhere else. New defender did not inform me of trial date, so, I missed court and had to repost bond. Upon arrival at new court date the new attorney seemed to be completely unaware of my 18 month battle with the case and rushed me and half way thru a statement to bring him up to date he hurriedly left the room and came back motioning me to enter the courtroom at the bench. He and the prosecutor began telling the Judge of a plea agreement and I don't remember anything from that moment until I exited the courthouse. I think from the stress of that I shut down. I received a sentence of felony resisting arrest, 4 year jail, 5 year probation of an incident I was innocent of. What can I do. HELP.