I've had SPD since I was 19 weeks pregnant with DS2, who is almost 18!
Firstly, The Pelvic Partnership might be able to put you in touch with a private physio in your area who could help you. I, personally, have heard better results with osteopaths.
Your toddler will understand that you can't get on the floor, they can't climb on you etc. It will be difficult at first, but they will get it, DS1 was 20 months when I first got it, he understood quite quickly.
Your physio might be able to get you to use crutches, there are many different types, not just elbow ones, because it might be the only way you can stay mobile. I ended up in a wheelchair, and was in and out of hospital.
Keep taking paracetamol if you can't take the codeine, take it regularly. Don't miss a dose, it is surprising how well it can control pain.
Ice the joint. I freeze water in condoms (cheap ones from Lidl) because they are small and not heavy. They provide a lot of relief.
Get a body pillow. They provide a lot more support than a pillow between your knees.
Do not walk up and down the stairs more often than is absolute necessary. When you do put one foot on one step, bring the other foot to that step, so both feet are on one stair and repeat.
Rest as much as possible. No hoovering, pushing buggies, or shopping trollies.
Some women swear by Snoozles. I've not tried them.
If you can get some satin pyjamas are brilliant for turning in bed.
Rope in as much help as you can.