Ultrasound without OB prescription

Hi mga mami! Ask ko lang, first time mom here! Last ultrasound namin ni baby is 8wks as per OB request. Tapos nun nagcheckup kami last Saturday sabi ni Doc ko, 24wks nadaw next ultrasound namin for gender. Want ko sana makita si baby sa 12wks namin, kaso yung iba sabi wag na ko paultrasound kasi wala naman sinabi si OB ko. Kasi masama dn daw lagi ultrasound. #pregnancy #advicepls Any suggestion po? Thank you!!