Sad and confused

Hi everyone, just wanna asked what happened and kung may nakaexperience na din po ba ng ganito. 10 days po delay period ko. Last Mar. 16 i took pt and the result was positive, then on Mar. 23 still positive but later that week, I bled, brown to bright red with small clottings. The bleeding lasted for 6 days. I have gone to the OB twice already and they said they couldn't find any gestational sac sa ultrasound. No embryo was developing sabi. Then on April 6, nag pt po ulit ako and the result was negative na po. First baby pa naman po sana namin ng husband ko. What should I do?