Hello, from you what you say sounds like you had a pelvic injury during the car accident, that's why one of your hip is at a higher level than other. Your stomach ache and diarrhoea are not related to the accident. Stomach ache can sometimes radiate to the back. You can get checked for both your problems. Take care.

Hi, Thank you for posting your query!

As per what you have mentioned it seems your are suffering for an whiplash injury of neck which occurs following accident where your neck bones moves backwards and forwards rupturing the joints and surrounding tissues. Depending on the severity of your condition you should consult an orthopedic for medications and physical therapist for proper rehabilitation of your spine.
Your major concern right now for me is your leg discrepancy, which shows pelvic dysfunction and due to this you can have back pain and walking issues.

Consult a Physical Therapist, he/she can guide you with some exercises and manual therapy for correcting your spinal dysfunction with proper screening of your problem.

Hope i have answered your query please feel feel to get back with further queries.