Irregular cycles/pregnant?

Hi there! So I only get my periods now every THREE months... it’s been like this for about a year now. I used to get regular periods. I don’t know why it changed. My last period was around July 25th and I now feel pregnant but all tests say no. Technically I haven’t “missed” my period yet though because if they’re still three months apart then it wouldn’t be due until October 25th. So could I be pregnant and tests just won’t show yet? Or what is going on! Ugh 😢 So frustrating. Dr appointment this week but just wanted to see if anyone else has had something like this.

Thank you,

Sam