What Causes Recurring Lower Abdominal Pains?

For the past several years I've been experiencing pain in my lower right abdomen. This generally occurs during intercourse at the moment of ejaculation. However, recently the pain has increased and comes without any physical activity, especially when sitting. More often than not it is very acute. My doctor has done x-rays, abdominal pressure checks, urology consults, and no one has an answer. I am 62 yrs old and very concerned!