worried about MC

im 15 weeks pregnant today and I was happy and not feeling worried anymore about the possibility of a miscarriage but I just came across a post which girls commented how far along they miscarried and someone said 13 weeks :/ im now starting to worry again . my pregnancy is normal last ultrasound I was 13 weeks and I saw my baby had grown alot and saw his heartbeat , im now 15 weeks and my next ultrasound isnt until im 18 weeks I hope my babys okay , grown and has a heartbeat still .  its so sad to hear these miscarriage stories .