Confused and Frustrated

Melissa • 25 and pregnant with our first little Peanut!
I've posted a few other topics recently. However, I'm 11 DPO, no sign of AF and experiencing very few signs of pregnancy or AF. I had spotting last Thursday for 3 days that was very light brown in color. But I've taken 3 hpt's and all BFN's. 
​I've felt off for the last week. Slightly nauseous with terrible heartburn. 
​I have heard of antihistamines causing negative results so I stopped taking my allergy medication. 
​Any insight?