I was for a 6 week scan today they said their was a heart beat and everything was ok I am still having pain and some brown spotting this spotting just started today any ideas what to do?

The last time I was pregnant I have some severe pain, I thought it was my period as I always had very painful ones, I was taking painkillers as I have very iregular periods and never suspected I was pregnant until I did a test at 5 and a half weeks, my doctor told me that the pain was my womb getting ready for the pregnancy.