Late with negative test

Jahayla • I have a daughter 12-20-14 and a son 01-07-19.

So my cycle averages 25 days and as of today I am 2 days late. I am still getting negative pregnancy tests. Could I be pregnant and not enough hcg to register yet? We have been trying for 6 months. My fiance has a vasectomy reversal may 30th. What's everyone's opinions?