Oh heck, I had the same, 2.5 yrs ago so dont remember to much but what I do is this, no walking that was the very first thing my physio said to me on the phone, scared the hell out of me! At night support your leg, ie on side put a pillow under the leg above to keep pelvis straight.
As for birth, you need to keep as active as possible, move around, yes to birthing ball because it will relieve the pressure, try to birth with gravity on your side, not on your back.Exercise is difficult to explain, its about strengthening your core muscles, pilates is essential afterwards, was highly recommended.
If I was you I would ring the ante natal ward, this is where your physio will be, you may be able to have a quick word. Explain your situation, if not try and see a physio privately, cost about £40 but may be worth it for birthing advice.
Sorry bit vague been a while, sleepless nights etc you know how it is. The best of luck