One of reason of this kind of pain is pelvic floor problems and weakness. Several organic and functional disorders of the pelvic organs, anorectum, and the pelvic floor musculature cause pelvic pain and back pain. One of the cause to be considered for your pain is levator ani syndrome. Ask your physician to consider this entity and get the following investigations;
2) pelvic and lower back MRI
3) nerve-conducting velocities and needle-electromyographic studies are used to help evaluate compression or entrapment neuropathy and pelvic floor function.
The treatment is following;
1) electrogalvanic stimulation,
2) biofeedback training,
3) digital massage of the levator ani muscles
4) sacral nerve stimulation
5) physical therapy for the pelvic floor muscles
Please read about this on this resource;
Pelvic congestion syndrome, Pelvic floor relaxation disorders, Pelvic floor dysfunction too need to be considered for the pain. Though treatment is essentially same.
Please feel free for your follow up questions.
I would be happy to assist you further, if you need any more information.
Thanks for using Just Answer.