Ang gestational sac talaga yan, mommy, pero normal pa lang na hindi pa clearly visible o measurable sa 4 weeks and 5 days, kasi sobrang liit pa talaga at maraming cases na mahirap makita agad sa TVS. I'd really suggest you follow up with your OB and ask directly about what they saw (or didn't see yet) kasi sila lang makakasiguro based sa actual ultrasound findings mo, better peace of mind na para sa iyo, at pwede ninyong i-plan ang next follow-up scan kung kailangan pa.