Late period

I'm currently 2 weeks late for my period, I have done 4 pregnancy test within this time frame - all negative. 
I had unprotected sexual durning my furtile window and day of ovulation, my partner and I have been using the pull out method until yesterday. I'm not currently ttc which is why I'm a little worried.
My friend told me that some woman don't produce enough hcg is their first trimester and can give negative results when in actual fact they are pregnant ?? Is it possible that I have tested to early ?? 
Any advice would be greatly appreciated, much love beautiful lady's 💚