What Causes Fibroid?

i have suspected fibroids as have had an internal and have been told that my womb is to large i have also been experiencing irregular menstrual cycles that are very painful , also i am booked for a pelvic ultrasound scan in about two weeks time , but i have found two weeks ago what feels like a lump in my cesareanscar on the right hand side when i start pushing at it it is becoming tender and feels like a hard mass ,i am worried sick about this i have had to c sections and been cut in the same place.. what do you think? many thanks