Why Am I Having Slow Fetal Growth And Brown Spotting After A Miscarriage And Positive Pregnancy Test?

My marriage on January 03rd this year.I had my first periods February 03rd after my wedding.Month of March I didn t have my periods.When I test it was show me pregnant.But uncertainly March 28 I had bleeding with severe pain.And the next day I had miscarriage.After this I didn t have my periods again on April.It also showed me I am pregnant. Doctor suggested me vegeston 200 tablet for one month from my first ultrasound.I followed it and again I went to my scan after one month. He said that baby s growth is slow and asked me to have the tablet 2 weeks more.He couldn t find heartbeat. Now I am spotting light brown more than 1 weeks.There are only 4 days to go for the scan he asked. I am really scaring about it.Please explain why I am having this problem?