www.pelvicpartnership.org.uk
Has lots of useful info.
Is there any chance of you seeing a physio before the birth? You could really do with one finding your pain-free gap (which is basically how wide apart you can open your knees without it hurting) so that you don't go above it and damage yourself in labour. Especially if you have an epidural, and therefore can't feel it hurting.
You should also discuss with a MW about positions for giving birth to minimise damage to your pelvis. Lying on your back pushing is likely to not do you any good at all. You should be trying to keep as active and upright as possible through labour... which may well be easier if your pelvis has opened already :-/
Heat and cold can help the pain, baths too, but BE CAREFUL getting in and out. Keep your knees together as much as you possibly can.
Don't do too much after the birth. I was pushing a massive pram around and knackered myself. Then when I started feeling better (and fat) decided to start doing sit-ups, which set me back a long way. It can, however, just vanish after the birth... but if it doesn't, you need to see a physio.
If you don't mind me asking, who told you that you have a separation, and how wide is it? The reason I ask is that the joint may just be misaligned, which a physio can sort for you very quickly.
Lots of very knowledgeable people on here, you're sure to get some good advice.
Hope you soon start feeling better.