Bleeding after Sex!

I found out I was pregnant on May 16. I am 8 weeks and 3 days now on June 12. My partner and I have only had sexual intercourse 3 times since we found out I was pregnant because each time we do I bleed. We tried last night for the third time and I bled so much afterwards. It is the ONLY time I bleed during the pregnancy. I went for my first doctor visit at 7 weeks and the baby was perfect. The doctor said I have a mass or something (I can't remember what it was exactly) that is most likely the cause for the bleeding after intercourse. Is anyone experiencing this? It's so scary for us that we decided to refrain from intimate relations until we see the doctor again on July 9!