Feeling guilty about stopping giving my baby breast milk..

I tried breastfeeding and it wouldn’t work out, so I started exclusively pumping and that turned out to drain the absolute life out of me. Not only was it physically exhausting, but mentally it did not put me in a good place. I switched my son to only formula and I feel like ever since, it has been a nightmare. He’s having trouble pooping along with other things. I just feel like he was a much happier baby when I was giving him breast milk. I feel so guilty. My supply is pretty much dried up and I also vape so I can’t even switch back to breast milk. I feel like such an awful mom & I feel like I’ve failed my son.