Think I've made a mistake

[2duck]

I posted on here last week about our new puppy. Thing have improved a lot - she will sleep by herself at night now but she hates being left alone during the day. I've tried the gradual approach and it doesn't seem to help. She is happy in her crate if someone is around but howls and wees if no one is.
I knew having a dog would be hard but I hadn't realised how all encompassing it would be. I feel like I'm not being a proper mum to my DCs because I have to deal with the dog. I actual feel pretty depressed, similar to PND I had with DC1, and don't think I'm cut out for having a dog and feel a bit like I've ruined my life. My DCs would be devastated if we got rid of her and my DH thinks we should stick it out but they're not the ones with her all day not able to leave her to even put the bloody washing away.
Everyone keeps telling me it'll get easier but I dont feel any bond to the dog at all. Has anyone kept a dog after feeling like this or anyone who did decide they weren't cut out for it. Please be kind as I feel quite on the edge 😥

My DDog had separation issues as a puppy. I remember trying to leave to take DD to her swimming lesson. DH was due home about 10 mins after we had to leave the house for the lesson. dog was about 4 months old. I had treats ready, his comfy cage that he slept in at night, we'd been practicing leaving him for a minute or two at a time. He was screaming so badly by the time we got in the car I had to go back in and wait for DH to come home. We missed swimming.

We then went to not leaving him at all. It drove DH totally mad that I insisted the dog came everywhere but I figured leaving him so upset and scared would make him worse. He slept in his crate in our room (always had done) and as I work from home it wasn't too bad not to leave him.

He is now 16 months old. We can leave him for 4hrs, pop in for an hour and leave him again for another 4hrs. He doesn't get upset, he just snoozes on the sofa. We rarely leave him more than a couple of hours (and even then only on the weekend to take DD out somewhere). We moved house last weekend and he had that 1 day being left all day with just a lunch visit to let him out. I was surprised how well he did.

I am not sure how old he was when he started getting better - maybe 8 months old?

I hated the first month or so with our pup, found it really stressful and spent a lot of time crying and wanting to take her back.
Fast forward a couple of months and I absolutely love her and would be lost without her.
Things do get better, I promise.