Spotting after sex

Hi, i have an irregular cycle since i dont know when, it ranges from 50 days and my longest (and last cycle) was 96 days. Now, i am on my cycle day 20. We had sex (as logged) on my cycle day 5, 8, 12, 16 and 20. I experienced bleeding after sex during my last 3 sexual intercourse. yesterday i saw a line of blood on my underwear, I am also experiencing bad bouts of mood swings and on / crampings. I am scared, anyone who experienced these symptoms? When I told my doctor about this she doesn't seems to be worried at all..can anyone help me please. I am very scared about this, I am thinking and it feels.like it is impossible for me to be pregnant this time.