During the third trimester of pregnancy, your options for headache relief medication are limited. You should avoid anti-inflammatory drugs like Advil and stick to acetaminophen. You can take up to 1000mg four times a day as needed, with a maximum of 4000mg per day. If the regular acetaminophen is not providing relief, you can try acetaminophen combined with codeine, but this is usually used as a last resort. You can get this medication behind the pharmacy counter. If you experience nausea along with your headaches, you can try taking Gravol or ask your pharmacist about getting a prescription for Diclectin, which is specifically designed for pregnant women.