Do you think there is a chance I could still be pregnant?

I am in your exact same boat. My last period was the 19th as well. I've been having symptoms since the first few days of December. My AF was due today too, but nothing. I was researching the best time to test yesterday, and found that most of the time your body hasn't produced enough HCG until the 5th week of pregnancy. You should be 4 weeks and 1 day today. I would wait until Tuesday to test. You will be 5 weeks that day. That's what I'm going to do. Oh, I took a test (from the dollar tree) today and it was negative. I think it is just too early to tell. I know with my six year old son, I didn't get a positive until I was about five weeks. Good Luck. Let me know what happens.