Hi I M Sonali My Age Is 30 Yrs I

Hi i m sonali my age is 30 yrs i m pregnant now i have Now 3rd month when i was get pregnant i have lot of pain in stomach but also i have nausea headache, back pain means all symptoms of pregnancy so doctor suggest me for stomach pain to take 3 Months injection to not having in miscarriage so is it good for me or know is doctor doing this all is correct....