Thanks for your consult at DoctorSpring.
The most common lesions in the anal canal and surrounding areas are fissure in ano,peri anal abscess. But,the pain will not be in the buttocks. Buttocks pain can be due to musculoskeletal cause or neurological.
Constipation leads to hard stools and can lead to fissure. But,the pain will be more during and after passing stools.
In sitting posture,sometimes the nerves will have pressure effect and so there will be pain in their supplying areas.As you are diabetic,the pain will be aggravated too.
The nerves supplying the bladder will supply to other areas alos.So,while you are controlling the urination,there will be pressure effect of the other areas which are supplied by the same nerve and you will experience pain.
I prescribe muscle relaxant tablet,B complex with B12 ,Rejunuron tablet to my patients with similar complaints.
You can try these with the advice of your physician/Surgeon.
If the symptoms does not subside,get an MRI of lumbosacral spine so that any compression of the nerves will be seen.
Do physiotherapy or slow walking.
Hope this helps, please feel free to discuss further.
Dr Haricharan Perigela