TTC - Missed Period

Just needing to vent.. maybe some encouragement. I’m 12 months pp and we have been trying to conceive for about 9 months. For the last 15 years, Ive always been extremely regular… only ever having been late by more than a day or two, when I was pregnant with both of my daughters. I’m 6 days late but tested negative several times, on different days. For the last 4 days, I’m extremely fatigued and sore. I’m just wondering what might be going on that I’m suddenly missing a period after never being irregular, but not being pregnant and still having symptoms?

We had a really hard time getting pregnant with our second child so of course when I got my hopes up that we were pregnant again and then tested negative, I can’t shake the disappointment.