What Should I Do?

Hi. I had posted once before the situation I was in. I'm not sure how many of you guys read it but busically the story is that im 16, with a boyfriend of 8 months that I care for more than anything. The real story is that one day I got drunk with a few guy friends and one of the guys took advantage of the situation. We ended up having sex and we didn't use protection. I was a virgin before that day. I wasn't sure if I was pregnant and to tell you the truth i'm still not. I thought my period had ended the 6th of jan. And I was basing everything I thought off of that date. I took a pregnancy test yesterday morning and it came out negative, but I still hadn't had my period. This really confused me. I investigated dates more and realized that I actually didn't start my period till the 8th and I ended on the 12th. That means that I could have possibly been ovulating (i had sex on the 20th) and if so there's a higher chance of being pregnant. This also means that the pregnancy test I took isn't accurate.... Right? I'm not expecting my period for a little less than a week. Could that test have been accurate or was it a complete waste? I'm really worried right now because as of yesterday morning I was done worrying about whether I was pregnant or not and stated focusing on making my relationship with my boyfriend work out. If somebody could please respond with any.... I mean any feedback on the situation, it would be greatly appreciated. Thank you for those of you who read this. God bless all of you.