Mama, please see your doctor soon, especially if these three are happening together regularly. It's better to get checked para ma-rule out kung ano talaga ang cause, kasi headache, heartburn, and nausea together can mean different things. A few of us mums have experienced similar, pero iba-iba ang reasons, some pregnancy-related, some not, kaya really kailangan ng proper check-up. Don't worry, pero don't wait either, okay?