Have had a cin 3 reading b4 & had loop biopsy proceedure done but having pain after sex now & heavy clotting..could it have returned?

Not likely.: You've just had a cervical biopsy. This is a procedure where some of your cervical tissue is removed. It grows back and there's no harm but it can result in bleeding over the short term, especially if you've resumed activities like intercourse soon after. So try to take it easy for a few days and it should be better. If there's still an issue or if you're still concerned see your doctor.