I know Penicillin will affect my contraceptive pill but can it cause breakthrough bleeding?

I have been on the pill for afew years now and i am in the middle of a 10 day course of penicillin for tonsilitus...my doctor informed me that it will stop my pill working in terms of contraception but can it affect my cycle and cause breakthrough bleeding? If so, will this stop after afew days when i stop taking the penicillin?