PID, or Pelvic Inflammatory Disease as it stands for, is a serious infection results in a painful swelling of the fallopian tubes and uterus causing potential ectopic pregnancy, infertility, and pain. This is commonly a complication of sexually transmitted diseases such as chlamydia. Fortunately it is relatively easy to treat the pain of PID using antibiotics and a heating pad.
Short Term Treatment
In the short term you can use a heating pad in order to address the pain. Place the heating pad on the lower section of your pelvis and this can make the discomfort far more manageable. Alternatively you can use other heat on the area such as a hot water bottle (but don't make it too hot). Of course using simply pain killers can help to a degree.
Long Term Treatment
In the long run you need to address the infection which will eventually result in the symptoms including the pain easing up. Normally the treatment for PID will be to take two oral antibiotics which will be chosen by your doctor. Make sure however that once the symptoms disappear you still continue to take the full course of antibiotics.
Failing this, if the pain persists you may require hospitalisation. Here the nurses and doctors will have many ways to help alleviate the pain including narcotic painkillers such as morphine if the pain is that bad. They might also recommend laparoscopic surgery in which all infected tissue is removed. This will relieve the pain but can also prevent infertility.