Ocella - I am taking sulfamethoxazole for three days. I talked to the pharmacy and they thought I?

You definitely need additional contraception (just to be certain).

The effectiveness of estrogen-containing oral contraceptives may be impaired by concomitant treatment with antimicrobial agents. Women using oral contraceptives should be advised of the risk of breakthrough bleeding and unintended pregnancy during concomitant antimicrobial therapy. Alternative or additional methods of birth control should be considered during and for at least one week beyond the last dose of short-term antimicrobial therapy, and for at least the initial weeks of long-term antimicrobial therapy when risk may be the greatest.

http://www.drugs.com/drug_interactions.php