I'm so sorry for your loss. It's still very early days and so I'm not surprised you're finding things difficult. 
Have you had any time off work? Would it be possible for your GP to sign you off work for a while? 

If the not wanting to walk past your Mum's was your only reason for handing in your notice, maybe some time away would be enough so that you don't have to change jobs. It may be easier to have the familiarity of your usual job whilst you're grieving. Speak to your HR department at work and explain how you're feeling. I think they'll want to help.

Take care

Debs