The delay is related to to a backlog in processing blood tests for drugs.
A first offense is not a crime in WI, so your Miranda rights, which aren't triggered by arrest, but custodial questioning, do not apply. You could be called as a witness against yourself at any trial.
If the test reveals any amount of active delta-9 THC in your bloodstream, you will be charged with operating with a detectable amount of a restricted controlled substance in your blood, which has absolutely nothing to do with impaired ability to drive, so not being high is not a defense. Depending upon what you admitted in what context, the officer's decision to draw blood may well be sustained by a court.
Your mistake in talking to the police about your use of an illegal drug is compounded by your post in this public forum. Stop posting details online, and schedule a confidential consult with a defense attorney. First offense penalties include the noted 6-9 month revocation, as well as a fine, and mandatory AODA assessment. You will likely also have to deal with an administrative suspension contest in addition to court proceedings.
This answer is provided for general information only. No legal advice can be given without a consult as to the specifics of the case.
Operating with any amount of a restricted controlled substance in your blood is illegal in Wisconsin, whether your ability to safely operate was impaired or not. You are required to be advised of certain rights prior to the administration of any chemical test. These rights are different than what are commonly known as "Miranda" rights. If in fact you were not advised of your rights regarding the chemical test, you may have an argument that the test results should be suppressed. Also, it is possible that if in fact five plus hours had elapsed since you smoked, the pot may not show up in your blood test.
If this would be your first offense for OWI or Operating with a Restricted Controlled Substance (or similar offense) it would not be a crime (no jail). And yes, it may actually take 9 months to get your blood test results.
In Wisconsin, marijuana is a restricted controlled substance. It is against the law to drive or operate a motor vehicle with any detectable amount of restricted controlled substance in one's blood. Therefore, even if you smoke five hours earlier, it is very likely that there is going to be some amount of Delta-9 THC still in your system. You are going to need a lawyer.
This answer is for informational purposes only. By answering this question, no attorney/client relationship is created. Although the legal information is accurate, it may not be appropriate for your situation. The best way to handle any legal problem is to seek the advice of an attorney.