Symptoms before BFP??

I'm still new to understanding my cycle, so forgive me if I sound stupid.
I think my fertile window was Dec. 12-17 or so. We had unprotected sex on the 12th.
AF is due January 1. 
I don't want to be pregnant, and I could be freaking myself out. But I definitely have light cramping, and my BBT is higher than normal (it's around 98.4 when usually it's in the high 97s after I ovulate).
Is it even possible for me to be having symtoms this early if I am pregnant? 
Can anyone give me some insight? I'm really starting to freak out.