They will revoke your probation and make you serve the remainder in jail. Depending on the county and whether or not your probation was a misdemeanor or a felony, you could qualify for 2 for 1 on good behavior.
Jail is a terrible place. If you are this addicted to drugs that you want to do them even though you're on probation and the certainty of jail time, you need to do some serious drug counceling.
My bf went to jail for 2 months to serve out the rest of his probation. It was horrible for him, me, and his family and all of us that cared about him. We didn't even know he was using.