Mild pain on the left uterus & pelvis 3 months with irregular periods (was 28 days now 36-38)&severe pain before period. Miscarriage 8m ago. Causes?

See an OB/GYN. This may be early signs of endometriosis or potentially other issues. This can only be diagnosed with a thorough history and detailed physical exam, perhaps including tests and imaging studies, and possibly biopsies. Go and be seen. Hope you are better soon.