[paint.net wont llet me open my file]

I saved my file as a jpeg then it sayed it saved it as a jpeg but opens with pdn then i changed it to open with another program then it didnt work so i put it back to open with paint.net and it changed to a pdn file type and woulodnt open at all it says there was an unspecified error while opening the file and i spent 3 hours on it