Hello mam, Bleeding every time after sex is not to be taken lightly.
Most common reason for the abnormal bleeding pattern is a lesion of cervix
or some vaginal infection
But ever since you are having this for last year I think it can be due to some varicose veins
or arterio-venous malformation which has escaped from the vision of your gynecologist.
Get a colposcopy
done from some experienced doctor and see for reports.
All the best. Take care.