The worst thing that could happen is that your probation gets violated and you are sent to jail. However, being late won't necessarily result in a violation, especially since you blew .000 each time. Now, if you were 8 hours late, I think that would be a different story as it would appear that you were trying to "burn off" some alcohol before your test. I would wait until you see your PO and tell him why you were late, but only if he brings it up. He might not even know, so why bring it to his attention? From here on out, make sure that you are on time, even early if you can. Good luck.
In Michigan, when a probationer violates, the court can revoke probation and sentence to jail, modify the terms of probation, or continue the probation.
If the only thing you did wrong was show up late, that seems to be a minor violation. However, you should contact a local criminal defense attorney who can advise you on your judge's normal practices.
This is provided as general information. No attorney-client relationship has been established. This information may not be appropriate for the facts of your particular situation. You should consult with an attorney before taking (or failing to take) any action based on this information.