Please read! I need answers :(

So i had sex with my boyfriend a month ago, during my 3rd to the last day of ovulation. After 2 weeks I had my period. Is it possible that I'm pregnant? I've taken 10 PTs and a blood hcg test and all were negative. I've also read some comments on google that there were some that really had no HCG but still were 2- 6 months pregnant already. Is that even possible? Is it real? :( Help me!