I'm ttc irregular period so i'm observing my cervix for ov we had sex from start to end had spotting right after sex what can cause this

Multiple reasons: This can be caused by multiple things. Lower hormones can cause bleeding, irritation or infection of the cervix, pre-cancerous cells on the cervix (unlikely if your papsmears are normal). If your periods are irregular that could be the cause in and of itself. Would definitely recommend a full fertility evaluation. The irregular periods could be a sign of menopause coming.