By the sounds of it, you opened a dysfunctional marriage to polyamory and that blew up. Now you're once again dissatisfied with your situation, and you want to add more people, thinking that will fix the problem. I don't think it will, any more than getting a partner when you're single will fix any problems in your life.
If you feel like you're not getting enough from your partner, I see two options: make your needs known and try to have them met, or else do the internal work to make those needs less dire. Breaking up wouldn't solve anything since this is your personal issue, not a relationship issue.
I believe that adding people into any problematic situation is generally a bad idea. If it feels like something is missing from your life, that signals to me that you need to do some internal work to fill that void. Then if you still want to date other people, nothing wrong with that. But if I were the person being added into your life, I would feel a lot of pressure to make you happy, which is your job.
“As I am sure any cat owner will be able to tell you,
someone else putting you in a box is entirely different
from getting into a box yourself.” —bisexualbaker