Sayang, kantung kosong at 6 weeks boleh terjadi, tapi really kena check dengan doctor ASAP sebab ada few possibilities, bisa dating salah, bisa blighted ovum, or bisa timing ultrasound yang terlalu awal. Don't panic yet, but jangan delay, go see your OB/GYN soon so they can monitor properly with follow-up scans. Sending you strength!