Am I pregnant?

Hello everyone! I really need some opinions and advice! And if you ever went through what I am going through PLEASE feel free to let me know.

Okay, firstly I just want to say I have a normal cycle. My period comes like clock work every month and this app really helps me. My man and I have unprotected sex and we did have sex 4 times during my ovulating cycle. I am not on birth control and we're not trying to have kids but if it happens, we will be happy. So last Saturday I started spotting which I believed was implantation bleeding because I had all of the symptoms. I had nausea, vomitting, backache, cramps, headache, dry mouth and loss of appetite.

I took a pregnancy test today, Wednesday, Thursday and Today but they all came back negative. I went to the GYN on Wednesday and took some blood work. The doctor did a sonogram and found nothing, she said everything looked normal. I got the phone call yesterday about the blood work and they told me that I was not pregnant. So of course I was a little bummed. My period was expected to be due today and I am never late. But it still hasn't come.

So I'm just a little concerned.

1. Could I be pregnant and the blood test couldn't pick up high enough amounts of HCG?

2. Did I really just get my period a week early?