Police Conveniently Forget Facts

I was pulled over by the police and subsequently charged with expired registration, driving on a suspended license and felony possession of methamphetamine and marijuana. The only reason stated by the police for pulling me over was because of the expired registration. However, my car had current year tabs on the license plate (the problem was that the tabs were not issued for that vehicle which the police wouldn't know unless they randomly ran my license). The police didn't charge me with the fraudelant tabs which is a more serious charge than the expired registration infraction. They didn't even mention the fraudelant tabs in their police report. This seems to be an indication that this may have been an illegal search and siezure.

They searched me twice. The drugs were not in plain view. The police had their hands in my pockets as they were asking me if they could search me. They didn't even give me time to give them an answer. Can the police randomly run your license and check the registration if you havn't commited any offense?

Please no judgmental remarks. I know I really messed up and am and will pay a huge price. Please answer the question as far as it is related to my case and the information I gave you. No generalized answers.

Thank you for your time
Felony in California

My cousin's car was searched in the boonies(PA) for no reason. He was afraid to refuse fearing that they would beat him senseless. The cops found nothing. It seems like the cops can do whatever they want and then find ways to justify it.
They told my cousin that he was driving funny!!??
Be sure to get a good lawyer....who could possibly use the info to plea bargain. Good luck!