I'm a sahm mom of 3, and I've always felt that kids need to know from day one that you can't pay attention to them 24/7. My husband travels 8 months out of the year or more, so it's usually just me and them.
Every day there are tasks I need to accomplish. Sometimes I work pt from home and I'm also a painter, so I try to get an hour or 2 in the studio most days. You HAVE to schedule, and you have to include your own time into your schedule. You HAVE to enforce "alone time" for him 20 minutes at time and enforce it (you don't say his age, but around 3 kids can entertain themselves if they have to). If you need longer, be strategic with movies etc to take his time longer.
A typical day for us is like this: I get up before them and do yoga. Then I get them all up and set them up with breakfast. I check email etc. I practice piano with my oldest while the other two entertain themselves (had to enforce that at first), then we do some sort of lesson or book all together, then we do errands, and lunch together. Then the baby goes down for a nap, the older 2, (3 and 5) have to entertain themselves while I work or paint for a couple of hours. I check in on them, give snacks, etc but pretty much do my own thing. Late afternoon, we all do something fun for them, like the park or something. Then I set them up with dinner, and if I need time for bills or some cleaning, I let them watch TV while they eat and I do it. Some days we all go to the gym for me to do 6:30pm Zumba or something and they play in the daycare. We come home, read books, they go to bed, and I have a little alone time. I read adult papers and books and stay on top of politics etc.
So as you can see, that isn't totally child centered. All my kids are super independent and able to entertain themselves, but I had to force it when they were young and wanted constant attention. I have always enforced etiquette if I'm on the phone, and I talk to my adult childless friends all the time. If I need to ignore the kids and get serious house work done now and then, I do it. I listen to whatever music I want in the house-I loved "adult" music when I was a kid. They are content to play "near me" and they already have their own chores to do too. Sometimes I just check out and watch a French film on Netflix. It's so boring to them, they just play.
I know it's easier with 3 than one since they entertain each other, but I did the same when I only had one. Sure at least several times per day I really focus on them and do "their stuff" but not all day long. I'd go nuts. Plus, since they know I can't "always play" they're super thrilled when I come over and play.
It's such a luxurious cake walk compared to the FT career I was in for over 15 years before having kids. I may end up having to go back to work, which also helps me "savor the time".
Sounds like you are doing too much kid stuff! Take back some adult activities and themes in your day. Try to get your schedule under control and hang in there!