7 dpo

Hi there! 
I am 7dpo and I just feel flat out weird! 
I have been cramping and having lower back pain since 4dpo. Also, my nipples have been sore almost immediately after my O date, and since then feel heavy and hott. I now feel "tinges" and pinching in what feels like my uterous. I am feeling a "butterfly" sensation in the stomach, along with pressure in my pelvis region (not to mention heartburn!!) The most confusing symptom is my increased heart rate of around 96bpm, which is high for me (it feels like my heart is pumping out of my chest). My temp is also a bit higher. Am I going crazy or can symptoms of pregnancy start this soon?!
Mind you I never PMS like this so that's another weird thing.