Is refusing to let the police search me an admission of guilt?

Absolutely not. Under the 4th Amendment to the US Constitution, you have an absolute right to prevent a government from conducting any illegal searches and seizures without a warrant. Furthermore, under the 5th Amendment of the US Constitution, you have an absolute right to remain silent, and in both instances, your refusal to allow the officer, or to search you, or for you to make any statements cannot be used against you in court.