Hey mama! Oo, totally normal yan sa third trimester, maraming moms experience headaches around this time kaya hindi ka nag-iisa!
First thing I'd check is kung sapat na hydration mo, someone in my mum group swears by drinking tons of water and even adding magnesium drops to help, and sabi niya nag-work talaga for her. But heads up, sometimes headaches can also signal blood pressure changes, which is something doctors like to monitor in the third trimester especially. So if the headache keeps coming back, gets really bad, or may kasama pang swelling or blurred vision, worth checking with your OB talaga para peace of mind mo.
For now, rest, hydrate like crazy, and don't stress yourself out, third trimester hormones are wild! Let me know if it gets better with the water intake. Rooting for you!