i'm convinced i am pregnant

i am 17 years old, and have been having sex with my boyfriend for 7 months. I am on the contraceptive pill microgynon. last month i missed the first day of my pills after my period and took 2 the next day and on that day i stupidly had unprotected sex. Since then i'm convinced i am pregnant, if i was i'd be six weeks pregnant by now. I have not had any symptoms such as sore breasts, morning sickness nothing. I have had both of my periods that were due since then although they have been slightly lighter than my normal period and lasted 5 days, with the 4th day being very heavy with dark red blood. My nipples have not got darker but i have noticed that the veins are slightly more visible but this only occured when i was due for my period. I checked my cervix and it was low and hard with a dimple which i read up closes during pregnancy, mine hasnt. I keep thinking i am pregnant and am scaring myself, any advice ?