Need advice

I’m extremely confused. My husband and I are TTC. Month 2 for us now. My periods are regular. Like clockwork. I start on the day I’m expected to for literally my entire life other than when I was pregnant with my son. This month I had all the pregnancy symptoms as in nauseous, extremely fatigued etc. but time came and it was time to test and I keep getting negatives. Now I’m 4 days late. Which has never ever happened. What could be going on??