Know how you feel. 3yo DS here, work three days a week, plus a DP that walked out a month ago when I finally confronted him about needing more support .
Its easy to say but can you list action some things that would help? Obviously a free week at a health spa would be top of the list but if you are anything like me this is a pipe dream. However, your need for some 'me' time is important as it sounds like DS and 'the house' are draining you.
I have:
Enrolled DS into preschool two days a week when I am not working, I feel a bit guilty but he loves it!!
Eased up on letting him watch TV/Cbeebies sometimes to give me a break.
Finally gotten over guilt of asking friends and family to heve DS overnight sometimes- they love it, he loves it- I love my night off. Could your DH do this for you also?
Found a gym with a creche.
Asked friends over for dinner / DVD, beats being in alone every night!!
Good luck....
Researched more things for DS and I to do together locally- have found football and craft activities that I was previously unaware of.