The best way to withdraw from cocaine is under medical supervision so that you can process cravings and avoid relapse. More strategies for how to withdraw from cocaine here.
Help for meth addiction includes detox, physical stabilization and pyschological treatment. More on getting help for meth and where to find it here.
Yes, contrary to popular belief you have the potential of becoming addicted to THC. Studies report that THC use can lead to dependence and heavy use can result in withdrawal symptoms when you stop using THC. More on the addictive properties of THC here.