Early Pregnancy?

I'm sure you get these kinds of questions all the time, so I first want to apologize if my question is a repetitive one. I read the post on symptoms, but my situation isn't quite the same as any of the other ones I read.
I'm 16 years old and recently lost my virginity to a long-term boyfriend on feb. 3rd. Altogether from that time until feb. 13th we had had sex 4 times, on the last time the condom broke [condoms were used all 4 times but we didn't have a problem with the first 3.] the day after our little mis-hap I went to a clinic for the morning after pill, but since then my period hasn't come. [it was due around mar. 5th] i've read that the morning after pill can sometimes effect your peroid cycle and other than the missed period I don't have any symptoms [breasts are fine, no pain. Eating is regular. And i'm still very energetic without stomach complications.] I would now be 5 weeks pregnant if I had concieved any of the 4 times. I also took a pregnancy test yesterday that came up negative. For those of you who are pregnant, am I expecting symptoms too early? Any insight would really help a lot, i'm pretty clueless :/.