I don't know the details of your condition but I have a chronic and painful rheumatic disease which mainly affects my spine and pelvic joints although also affects other joints eg wrists, knees, shoulders...
I can tell you the things I did/have done/am doing to help (my DS is 21months):
Get as much help as you can - we've ended up with an au pair but we have no nearby family. If you are in Homestart area they may be able to help.
Put baby in an extra t-shirt rather than a popper vest.
Move everything you need for day time baby care downstairs. e.g. changing station. Put it at a height which is comfortable. Put the cot up on bricks so you don't have to bend so low to baby.
Buy a hippychick hip seat and wear it when carrying baby - this distributes the baby's weight much more effectively.
Get a referral to your community occupational therapist who can come and make adaptations to your home to help. Mine arranged various things e.g. making my front step in to a ramp to help with the pushchair, getting a ramp made for the car to push the pushchair in to it without having to lift it etc.
Get someone else to bath baby.
Invest in a low chair/stool to enable you to play with your baby on the floor rather than having to sit on the floor. A toddler's chair would be good for this and in time your child can use it.
I'm sure some will tell me it is unsafe but it worked for us: I had DS baby gym on a blanket on the dining table hemmed in by the dining chairs so that I was picking him up/putting him down/playing with him at waist height until he rolled - fortunately for me this was very late at 10 months!
Leave the car seat in the car so you are only lifting the weight of the baby. if you need to transfer it to the travel system have a look around you and ask a stranger - dads are good. Don't be embaressed just say "please can you help me, I have painful joints and can't lift my baby seat". I do this LOADS and 99% of the time people are very willing to help.
Go to a physio and ask them to show you what position to do things in so that you stabilise your joints e.g. changing a nappy/using the car seat/pushing the pram - I had a brilliant physio who just by showing me different positions in which to do things really helped me.
In time:
Use a booster seat with tray rather than a high chair as this is easier for lifting baby in to/out of. Also it's not too long until they can be trained to climb in to it.
As soon as possible teach your child to climb the stairs by themselves and to come down backwards.
Get them in to a bed early as they can climb in/get out without you lifting.
Get a rotating car seat which puts much less stress on your pelvis getting the child in to. And in time they can learn to climb in to it themselves.
But the biggest single thing that will help is not being too proud to accept help. Save yourself for the fun bits e.g. playing but wherever possible get someone else to lift. So at clinic ask the HV to lift. When you have friends round ask them. When in town ask a passerby. People are normally very willing to help if you ask, but would be embaressed to assume.
Hope that helps a bit and good luck!