Bleeding ?!

Ok so two night ago I had a stressful day at work I came home and went to sleep my partner woke me up when he got in from work..  I went to the toilet and there was red blood in my pants 😭 I rang 111 and was told to go to docs the next morning, the bleeding wasn't heavy and it was only when I wiped it quickly turnt pink then brown . I had NO pain when this was going on, when I went to the doctors the next day they listened to baby's heart beat and said it sounded very healthy. Has any one els experienced this?and have any idea what it could have been?  I'm 12 weeks pregnant tomorrow. Any replies are welcome 
Thank you .