Ay, I feel you, labs and ultrasounds can be expensive talaga, lalo na kapag repeated visits! Honestly, best thing is to ask your OB directly kung saan siya usually nag-refer ng patients, kasi maraming clinics ang may partnerships so mas mura sometimes. A few of my mum friends from Taytay and Pasig area swear na ang mga government health centers ay sobrang affordable for ultrasounds, so try Taytay Health Center or the barangay health stations muna, they do transvaginal ultrasounds din, and you can ask them for referrals to cheaper labs kung kailangan mo ng other tests.