Your perineum (region between anus and genitals) could have taken strain during your period of constipation and when trying to make a bowel movement you have strained this muscle in the process. Therefore, it is possible that you are feeling bruised and tender in that region and difficulty to sit for long amount of time. Unfortunately, like any muscle it will take time to heal itself.
Lower back ache, I am uncertain of.
Best of luck. Keep eating fruit and veg,
A hemorrhoid cushion may help you.
it sounds like you may have an internal tear in your anus, no doubt left from the constipation , my husband has what they call a fisher ? which is a cut in the anus, and as the back end is being used regularly it is constantly opened and doesnt get much of a chance to heal.He experiences pain in his urinary tract aswell and similar symptoms.The doctor can check this out for you.it will heal in a few weeks but unfortunately can easily come open again.It is not forced to bleed. The doctors can prescribe a cream for the discomfort which stops any bleeding should it occur, however the husband says to use pea sized amount only as it is absorbed straight into the blood stream and too much makes you feel really ill very suddenly .Try to keep your fluids up and maintain regular bowel movements. Keep yourself loose to enable your body a better chance of healing and lessen the chance of catching it again.Good luck x