Aww mama, I feel you, pregnancy is really unpredictable, ikaw pa lang naka-28 weeks at parang nag-uwi ka na ng sampung libo! Mild headaches are pretty common sa third trimester (hormone changes, weight, dehydration, all of it talaga), pero ang parang mainit na hininga combined with how sick you've been... I'd really suggest checking in with your OB just to be safe, lalo na since you had all that vomiting at stomach pain last week, hindi ka alam if connected lang lahat or something else going on, kaya better to confirm. Your body is working overtime, mama, so hydrate like crazy and rest when you can, pero doc visit is best para peace of mind mo and baby's.