Sometimes blood in discharge after orgasm, usually brownish in colour. what causes this? have some spotting gyno has advised likely hormone imbalance

Bleeding after sex: Color of blood varies based on how fast you are bleeding - brown if it's slow & red if it's fast. Bleeding after sex can occur: if you are about to start or just ended your period or; around ovulation; have inflammation on your cervix; if you have something in the uterus like a polyp or fibroid; or from a hormonal imbalance; or post menopause. You need to see your Dr again for evaluation.

Cervicitis?: New, abnormal or unexplained vaginal discharge and/or bleeding needs professional evaluation. My guess is it's triggered by sex itself, not orgasm. Bleeding after sex can be due to cervicitis, often caused by STDs (chlamydia, gonorrhea). If not checked for infections, especially STDs (if at risk), that's an important step. Discuss w/ your gyn, or maybe consider second opinion at an NHS GUM clinic.