Can’t find the creak, going crazy

I’ve taken my entire bike apart, cleaned and regreased everything. I even made a post in r/mtb that I solved the creak! lol. Well I thought it was my seatpost, so I went back and cleaned the seat tube of any remaining grit and really greased it up. Creak was gone for maybe 5 minutes into my ride. I thought it must then be my saddle, nope. Pedals, nope, suspension pivots, nope. Stem, nope. Bb or cranks, nope. The noise only happens when I press on the back of (any) saddle, and the creaking seems to come from the top tube (I can feel the clicking there the most). Then I discovered it is made worse when I pressure my left pedal while weighting the rear of the saddle. But it doesn’t make any noise if I weight the right pedal while pushing the back of my saddle… wtf?!!! And it makes no noise when pedaling out of the saddle on either side, or any noise if I just compress the suspension without touching the saddle. Is it possible it’s the frame itself flexing?

I need the power of the reddit hive mind, as I am losing my mind every time I ride – it’s super loud.