I'm late, But...

Tt
I'm still taking the pill, I was planning to get off of it by the end of January. We Also use condoms on my "most fertile days". 
I took one of those cheap $.88 pregnancy tests today And I believe it was negative. It was not first morning urine but I never did My first morning urine With My other two kids... 
I'm a Little anxious because I have been having heartburn and execive salivation... I feel different But I might Just be overthinking. 
What should I do? 
FYI I got pregnant With My other two while on the pill so I'm very confused.