Wah, tu soalan yang common betul! Honestly, beta HCG levels tu very individual, ada mummy dengan singleton yang level tinggi, ada yang rendah, so it's really not a reliable way to confirm singleton or twin. The best way is ultrasound scan je, even at 7-8 weeks dah boleh nampak clearly kung ader satu atau dua baby. Anyway, rasanya better you check dengan doctor kau since everyone's hormone levels beda-beda, and they'll know your specific situation best!