@KateyKube
You’re really really not basically a single parent.
OP- I’m a LP too. DS is almost 3, I separated from his dad when he was 9 months. Started off being very involved and has now trickled down to weekend visits (in my home) probably every 2-3 months?
After DS (like you,always my number 1 priority) my career is really important to me, and my job is full on, so I get quite a lot of “life satisfaction” from my job- but that feels a bit wrong too tbh. Like between my job and my son, I get lost somewhere?
I moved back to my hometown as London was unmanageable as a LP to a baby, for me, and I’ve made no new friends, been away too long to pick up with old ones, and my family have proven collectively useless as a support network. I go out maybe once every 6 months? Always a work related function. Travel for work occasionally but have to be “on” 24:7. Can’t remember the last time I went shopping, for a hair cut, to a yoga class, to the gym....no I can! It was 2.5 years ago 
I totally hear you. It’s so hard. It feels relentless. And it feels unacceptable to say- but I’ll say it. My child is the bright sun in my sky. He’s my life’s joy. He is my first and last, and everything in between, in all things.
But fucking HELL Im glad nobody told me my life would be consumed this way before I found myself here. I wouldn’t have thought I could stand it. Thank god he makes it worth it.
Still - I do mourn my life Before and wonder who/what I’ll be After he stops needing me.
Solidarity 