As a contractor how do I work on multiple client networks without data leakage?

I am a contractor who does development for more than one client. Let’s call them Client A, Client B, and Client X.
I use my own laptop for all 3 clients.
Throughout the day, I have to work on and respond to emails and instant messages about projects for all 3 clients.
In order to work on Client X’s project, I must be connected to their VPN.
Client X performs SSL deep inspection on the traffic on their network. (I get errors from sites/apps that enforce key pinning)

I’m worried that information about Client A and Client B, (not to mention my own sensitive information) might be exposed to Client X. How can I prevent this, but still maintain my ability to communicate with A and B while working on X’s network?

I’ve tried giving each client its own VM on my machine, but the hefty resource requirements of the software I have to use (IDE) makes this prohibitively slow, to say nothing of the licensing difficulties.