You ask a very astute question. Yes, sexual abuse is a common cause of painful intercourse. When a person has been sexually violated, and has not worked through the feelings attached to the trauma, the physical pain that remains serves as a reminder of the wound that was inflicted as well as reminder that that wound is still waiting to be healed.
Psychotherapy (talking therapy) is vital to work through the feelings that are expressing themselves through the body. Also, alterative therapies such as acupuncture, polarity, and cellular memory body work can be effective in releasing remnants of the trauma that are actually 'trapped' in the body.
As for whether a short vaginal canal could cause pain. I suppose it is possible for a woman with a short canal to feel cervical pain when she is being penetrated by a man with a very long penis. However, a sore cervix is often a sign of infection and should be checked out by a gynecologist.
Many women with short canals are able to accommodate long penises by adjusting their intercourse positions so that penetration is less deep. Rear and side entry positions provide less deep penetration than do missionary (man on top) and female superior (woman on top) positions.
Keep asking the right questions and feeling your feelings and you will get to the bottom of the cause of the vaginal pain. Best wishes for a swift recovery.