Uy, 16 weeks ka na! Dizziness sa pregnancy is pretty common kasi lumalaki ang baby at ang demands ng body mo, pero since ikaw ay nag-aalala I'd really suggest checking with your OB just to be safe, baka low blood sugar, dehydration, o maybe anemia lang (maraming preggy friends ko napansin yan sa second trimester). In the meantime, make sure you're eating regularly, drinking tons of water, at standing up slowly from sitting or lying down. Fingers crossed it's nothing serious, but better safe than sorry with these things, mama!