18 and pregnant? please help!

My last period started November 9th and it lasted until November 13th. I had unprotected sex on November 15th in the am. On November 16th I took the morning after pill around noon. My doctor told me that if I take it after 24hrs it won't stop a pregnancy but I went ahead and took it. But I also know that the first two days after your period are your most fertile. My symptoms are I cramped one day and that was it, I'm extremely tired all of the time, I feel like I'm more dehydrated then normal, I've been craving tap water over my propel water, last night I experienced nausea and today I used orange dawn doshsoap and started gagging. I've taken 4 pregnancy tests but all of them say negative. But I also know that some women don't produce enough hcg to show up on a home test. What are your thoughts? I'm currently 9 days late. I was supposed to start December 9th.