If i keep taking penicillin will it keep the infection in my tooth from spreading ?

Yes : Antibiotics are a temporary measure to keep the infection under control. You must see a dentist to treat the underlying problem.

Yes: But you must treat the source of the infection. You cannot take antibiotics forever.

In the long-term, no: If a doctor has prescribed penicillin, then take all of your medication as directed. But, if you are taking antibiotics long-term on your own initiative it will not benefit you. You have to treat the cause of your dental infection, otherwise, extended antibiotics can suppress your immune system, cause resistance, & make you susceptible to fungal infections & GI problems like vitamin deficiency.