It gets better... right? Coping advice?

FTM. I just really need to vent at this point. I've been very lucky that my first and second trimesters were relatively easy and uneventful, I've been counting my blessings. I knew the third one was likely to be uncomfortable, but I was not prepared for what has actually happened.

As soon as we've turned 28w, things have started going downhill. I am fairly slim, I started showing early, and now my bump is massive in relation to the rest of my body (gained 4kg entirely into it in the last month). It doesn't bother me, except that now my upper abs feel like they're being ripped apart in literally any position I take except lying down with bump supported. The pain is not relieved by physio exercises or painkillers, but I managed... Now that I'm in the middle of my 29th week, though, I've been blessed with upper back pain that doesn't subside even when lying down. My pelvis is fine (for now), funnily enough... But I went from doing 10k walks every day to barely being able to manage a 15 min walk - it's just too painful for both my back and my abs. On top of that is the brainfog and constant hot flushes.

I just... I am not sure how to cope with all those changes and this pain. I'm supposed to be working (WFH behind a computer), but I can barely manage to sit straight for more than 5 minutes. My job is very mentally taxing, but I'm struggling to form thoughts most of the time and I end up taking long naps cause I need them as my nighttime sleep is ruined. I can barely leave the house, and even basic chores now feel impossible without help because I keep needing to lie down to relieve the pain. I am also now quite emotional as feeling overwhelmed by all this - the guilt of being useless, the loneliness of being cooped up at home, and the thought of having to endure it for the next couple of months still while also mentally preparing for it to get even worse.

Has anyone had similar pains in their 3rd trimester and found relief through exercise or some other means? Any words of wisdom or advice? Thank you all for reading, I hope you are doing well.