Sent for scan

3 years ago I had cin 2-3 removed by letz treatment. I've had a baby since then and been on depo injection for 6 months the last 3 months I have been non stop spotting and bleeding after sex. The doctor sent me to gynaecologist who had a look said all looked ok and she did a smear. A week later they gynaecologist secreta rang me and said they want me to go for a scan but didn't tell me why I can't get in contact with them so now I'm so scared does anyone know why they want me to have scan? X