Sabar mama, 6 weeks ni memang still very early, kantung baby kadang baru nampak jelas around 5-6 weeks, so timing tu boleh meleset sikit depending on akurasi ultrasound. A few of my mum friends went through the same thing and all turned out fine, tapi sebab ni touching on timing yang important, best lah you follow up with your doctor untuk confirm dating ni betul ke and book another scan dalam seminggu or two to see the gestational sac clearly. They'll give you peace of mind!