Needing parenting advice

This is probably going to be a long post and im not really sure what I’m asking just feeling really overwhelmed is allI’m a single mum of a 5 year old and 6 year old, always have raised them all by myself. I am a stay at home mum, all their life I have provided everything they ever need and want without any help from the father and I always spoil them take them out buy them stuff but very recently I’m finding as they are getting older I just can’t afford to do a lot of those things anymore and I’m feeling like a really crappy mum about it as they are getting older things are just so much more expensive but especially with the cost of living etc, lately I’ve just been feeling like the worst mum, my son refuses to listen to me, Swears at me nothing I do works not even smacking which is always completely a last resort, I could go on and on with my issues I’m just feeling so depressed burnt out underappreciated