I became a stay at home Mum 4 years ago. A few months after my baby was born I couldn't understand why my back and neck ached every evening. At first I thought it was our new sofa which is very squishy and tends to make me slouch but I then discovered it was my posture whilst using my PC at home. At work I had a much more practical desk and chair and I think I just got into bad habits slouching in front of the PC at home.
I have since bought a new, and more upright, chair and try to make sure that my screen is at the correct level.
I also found these tips on the internet which help keep back pain at bay. HTH.