At this age well its hard because they want you to play with. Some kids being more independent or not.
But keep to a routine. Daily. Over time, the child WILL get used to it.
For example: in my usual day, which is a lot like yours... my kids KNOW that at certain times I have "Mommy" things to do, and that that is when they play on their own. Sure I am around and supervise them... and I know their limits/abilities and attention spans, and I know and can predict when they will call me. I also KNOW how long I have.
But, when I announce "Okay Mommy has to work now... or do chores..." my kids know. They know that is when I am "busy." I PROMPT them, verbally. They know. BECAUSE it is a "routine" that "we" do.
Also, as my Hubby says: we all revolve around our kids. Sure, its the way it is. BUT... kids need to understand as they get older, that there is "adult time" too. Whereby the Parents do things around the house, or just do work. And then the child, will learn to respect that. For example: when he was growing up, at a certain time of the day, the kids would be prompted to stay in the playroom... when Mom was cooking dinner for example. It then brought sanity to the daily things the Mom had to do... and it taught the kids to respect that and to play independently. That some things just had to get done, and that they ALL cooperate and "help" in the daily scheme of things. AND... I am one who rushes around doing things too... major rushing around. Like you. Trying to do EVERYTHING before my kids call me or whatever. My Husband, being a "man" says to me: "The kids got used to you being there for every little thing even if they can do it themselves, and you taught them that... and you rush around like a mad-woman constantly & get stressed.... BUT the kids have to learn to just WAIT sometimes. And that you CANNOT be there for the constant little whims of theirs...." So... that is my lesson. He tells me: just tell the kids to wait. You are busy. They are fine. Its not an emergency. Its not going to damage them... just tell them no or wait.
And he has a point.
So I DO tell my kids "Mommy is busy.. you need to wait..." And they know that now. LOL
So, when he gets older, he can learn that. But you need to have a routine... so the child gets used to it and understands that. Realistically, we Moms CANNOT give our every second to our child. We have daily work/chores/responsibilities to do around the home. Both Mom and Dad. This doesn't mean leaving the kids by themselves, nor all the time... but 'teaching' them that everyone has a role.
And when he gets older, he can do things too, to "help."
Babies/toddlers go through a phase where yes, they don't want you to be on the phone or computer or anything... and they grab everything and type on the computer and get clingy. Both my kids did that too. So, you just try to distract them.
BUT if you have a routine about daily living habits, the child WILL realize that... and when older, they will know it. My kids KNOW like auto-pilot, that at certain times I do certain things around the house. All I need to do is announce that, and then I go and do it. I "cue" them. They understand. It brings lots more sanity to the whole daily rush of things. Things that Mommy has to do and cannot avoid.
All the best,
Susan