Hi, I'm 41, Have Had Severe Left Sided Abd Pain

Hi, I'm 41, have had severe left sided abd pain on day 3-4 of menses for two previous cycles, but not with last one. Family GP did blood work the first time it happened, found CRP of 98. I am currently day 14 of cycle. Cycles are irregular, between 21, 25, 27, days, last cycle was 28 days. Today, I passed a white ball of tissue, which was more like a mucousy string, mixed with bright red vaginal blood. This was during a bowel movement, but the blood was definitely vaginal. Still slightly spotting. What could it be.