I don't think it's cancer, more sciatica with the leg involve mentioned but get checked out anyway, no harm in hearing you have something simply treated.
Don't mess around with it any longer, we only live once
Your abdominal pain, your hip pain and your elbow problems do need investigating.
The hip and leg pain may be coming from the lower spine.
With regard to the "petechial" you need this to be investigated also.
You should tell mom to book you an appointment with the doctor to get checked out.