Ang frequent headaches sa third trimester ay common talaga, pero lalo na if it's one-sided at madalas, better to mention it sa OB mo on your next visit or call agad if napakalakas or may other symptoms like blurred vision or swelling. A few of us moms experienced this toward the end, kaya hindi ka nag-iisa, pero importante talaga na i-check dahil third trimester na kayo at gusto nating sure everything's okay with the baby and you.