Results from VCF?

So my boyfriend and I are in a LDR so when we see each other we get a little careless when it comes to protection. I bought some VCF from the store and I realized that the days I used them without a condom were spot on with my fertile days according to this app. Does anyone have any opinions to share about this product, especially how well it works? I won't exactly know if I'm pregnant or not until I take a test in a couple weeks... I like to talk about things that make me nervous.