I'm currently on doxycycline 100mg to treat chlamydia. dosage says one tablet a day for 10 days. is this correct because the pharmacy gave me 30 pills?

May be low: A more common dosage is one tablet twice daily. Check with your pharmacy and ask them to double check the doctor's orders.

Not correct: Once daily treatment isn't enough. The standard doxycycline treatment is 100 mg twice daily for 7 days. Did she maybe give you extra drug to give to your partner? (Ideally partners should be examined, tested and treated by a doctor. But it is common to use "expedited partner treatment" like this if partner is unlikely to see a doctor or clinic.) Check back with your doctor and/or the pharmacy.