I had PGP in both pregnancies and it was worse in the second. I'm still suffering with it (DC2 is 5 weeks old) and really hoping it fucks off soon.
I have to agree with physicskate, the only thing that makes it better is manual therapy (I also saw an osteopath but there are also some physios and chiropractors that do manual therapy and have experience of treating pregnant women) and it is absolutely something you should prioritise in your family budget even if it means scrimping on other things or putting it on a credit card.
Do look at the Pelvic Partnership recommended practitioners, also ask around locally (groups for pregnant women and new parents, antenatal/postnatal classes, doulas - they'll probably know of good manual therapists for PGP).
A support belt is only recommended after you've had manual therapy as if you have a misalignment in the pelvis (or anywhere else) it can make it worse.
You should also ask your midwife to refer you to NHS physio, mine was useless but I believe some are better than others depending where you are.
One thing that gave/gives me relief is being in water, hard to get the time to go to the pool when you have a 2yo (and with covid there are restrictions anyway) but if you could get to a pool it is lovely. Otherwise if you have a bath that's good too - just make sure DH is on standby to help you get in and out.
I understand how difficult it is when you have an older child. My DC1 is 3 and usually goes to nursery, but during the height of lockdown when nursery was closed and there were no groups, no indoor activities like soft play or anything, the only thing I could do with him was take him out for walks - which I couldn't do! It was very depressing and hard work. So do take consolation in the fact that yours is in nursery for 4 days and you only have to do 1 day - although that day is difficult. Don't feel guilty about extra TV time, you do what you have to do!
Oh and my DH had to do a lot more while I was pregnant and had PGP. He did nursery drop offs and pick ups, took DS out on bike / to park on non nursery days, did cooking and washing/clearing up... and was generally a bit of a hero. I did feel guilty at times but tried to remind myself that I was growing our baby which is a pretty big job!
Hang on in there. Pregnancy and PGP feels endless when you're in it but it will end! But do try and find the funds for osteo (or other manual therapy) if you can. I ended up seeing my osteo a lot and spending a fortune in total but it was worth every penny.