Ay nako, I feel you mama! That sharp back pain can really catch you off guard, lalo na pag unexpected movement ng baby tapos sumakay pa sa pregnancy aches, grabe talaga ang combo. At 20 weeks, yung weight distribution mo na talaga ay putting pressure sa back mo, so it's common, pero since it was that intense na nag-aray ka, better to mention it sa OB mo during your next visit para sure lang na walang concerns, okay? A few of my mum friends had similar episodes and most of the time rest, good posture, at prenatal vitamins helped, but doc lang ang makakapagsabi kung kailangan ng anything else for peace of mind.