Talk to Gynecologist on Low Serum Beta Hcg Test

I am 38 years old 1st pregnancy after 16 years already had 2 miscarriages heart beat start nahi hoi thy. Abhi 20 weeks ki pregnancy hay aaj report may serum beta hcg low aaya hy <1000 result aaya hay jub kay 20 weeks kay hisaab say normal range minimum 4000 hona chaheyea. Dr ko deakhaya aunhoo nay kaha k wapis beta test karwain and ultrasound karwa kay 1st December ko aaky dekhain. Im soo worried kay kahi miscarriage to nahi jo itna low beta result hay koi pain nahi hay and movement start nahi hoi hay plz help kay kia karna chaheyea.