Have you considered cysts which are quite common and when they separate you will have minimal spotting. You can have multiple cysts. Also, has your doctor considered endometriosis as a cause for the pain? Often, you have to have the surgery for an affirmative diagnosis. My daughter had sharp pains for years with little help from multiple OBGYNs. After 3 years, finally a Dr. took pitty on her and did exploratory surgery. She had 3 issues: 1) A staple from an appendectomy dislodged and positioned itself on the top of her uterus; 2) endometriosos, and 3) Her large intestine had scar tissue connecting it and twisting it at several points. Sometimes you have to push to get help. If you think there is something wrong, you may be right and you deserve treatment.
I hope you get this resolved.