Hi there, I had exactly the same as you - at 35 weeks, almost overnight,I went from having achy hips to being unable to walk without crutches.
This got worse and worse until I was induced on my due date. I had 2yo DS to look after, and I just couldn't do it in my condition.
Can you get someone to give you a hand after DH goes back to work? My dad stayed for a week after DH went back and that helped a lot.
DD is 9 weeks, and I was discharged by my physio this morning. I would definitely get a referreal for physio straight after the birth, and I'd expect your first session to be about 2-3 weeks after the birth. My physio was invaluable - I needed more than just pelvic floor exercises to get me re-aligned. I was on crutches for the first week after birth, then I hobbled for the second week. By the time DH went back to work I was functioning better, but on very strong painkillers.
I'd advise you to be pro-active about pain relief - it's not "good" pain or "functional" pain, so you might as well deal with it. If paracetamol or otc co-codamol isn't working then ask for diclofenac or the stronger, prescription only co-codamol (solpadol). If you do get solpadol, then ask for some lactulose to go with it, as there's not much worse than late pregnancy aches, a painful pelvis, and phenomenal constipation. Trust me.
Hope this helps, just remember it will get better!
Oh, and one thing my physio told me (you may have been told this already) is to clench your bum muscles when doing stuff that hurts your pelvis, particularly moving/lifting your bad leg - helped a ton with me, and you can still do that even when your pelvic floor is shot to buggery