Pretty much C/Ped from my April thread:
Hip circles
Pelvic tilts both backwards/forwards and raises side to side - these will strengthen your back muscles and the raises, if done by contracting your deep transverse muscles so pulling your ribcage to your hip using your side only, will keep your sides strong, which alleviates bump pain
Kneel up sideways on to the ball and stretch out your sides by raising the arm away from the ball over your head and pushing down on the ball for extra hip mobility put your leg out to the side to form a triangle (can be adapted for a fab waist toning exercise afterwards!)
To relieve pressure on your lower spine sit on the ball then leaning back roll the ball up your spine, keeping your knees bent to redress the curve you create by sticking your bump out!
Stretch your lower back by sitting with your legs apart and leaning forwards - particularly good once baby's engaged and doing this in a standard chair might be uncomfy. Also the squish of the ball means it's comfier for bump.
To help a head down baby engage and promote hip mobility (do not do with breech, transverse or SPD) squat so your heels are flat on the floor, your knees are bent double and lean forward onto the ball from as low down your back as you can manage - almost as if you're about to do the crazy yoga crow pose but with your arms out in front of you on the ball. Can also be done with the ball between your back and the wall if you can't get into a full squat.
Exercises on all fours:
Arch your spine like a hissing cat then pushing it down so you stick your bum and head in the air.
With your spine in a neutral position, hands directly under shoulders and knees hip width apart raise one leg, keeping your knee bent, and point your toe towards the ceiling. Hold for as long as you can. Repeat on other side.
Same starting position but extend one leg out straight behind you and the opposite arm out in front making sure you keep your hips parallel to the floor - put as much distance between your hand and your foot as possible by stretching out your back muscles. Variation: instead of holding the same position for as long as possible, bend your elbow so your forearm is at right angles, palm flat to floor hold for a slow count of 10, return to the stretched position for 10 etc.