Help please.....could I be pregnant?

Okay, soooo. Let me start off by saying, I did have my AF this month. I started on the 2nd and my AF usually lasts around 4-5 days. It was medium/heavy on the first day then spotting on the next. Only lasted 2 1/2 days. I then out of nowhere began to have a cold. I have been expirencing horrible back pain even before my AF arrived, I normally don't frequently have bowel movements. Like honestly it's always been normal for me to not have bowel movments every day. Past week and half Iv had bowel movements 2-3 times a day, also have lost my appetite, and I have become nauseous to strong perfumes and smells. making me at times feel light headed. I haven't even had a full on cigarette (I am a regular smoker) in the past 3 days because I can't handle the taste. Can someone please help me!! I tested 2 days before my AF arrived this month and got a BFN, maybe I tested to early? Please any advice or comments are much needed. I'm scared to run to the store and get a test because I fear it will be another negative...