My partner and I are poly, and lately I feel as if he hasn’t been giving me the attention I need. I don’t want to add any more partners at this time because I’d feel as if I’m using them to fill a gap and that’s not fair on anyone. What should I do?
First off, kudos for recognizing that other people aren’t need-meeting, gap-filling objects to be used to fix existing problems in relationships. To answer your question: talk to him! Bring this up openly and honestly. Focus on your own feelings without accusing him of anything.
Say that you would like to have more of his attention, and make some concrete suggestions for how things can change - maybe you two can plan a date night once a week, maybe he can agree to put his phone away when you two are hanging out - whatever works for you.
And talk to him about what’s going on with him to create this dynamic. Maybe he’s overwhelmed at work and needs you to hang on until a big project finishes. Maybe he’s worried about pestering you. Maybe he just had no idea you were feeling this way.
Friends and romantic partners, poly and mono, go through this occasionally. It’s rare to find that two people are always perfectly matched in terms of their social energy and capacity for attention giving. But if both of you can openly communicate your needs and take steps to getting them met, this is a very solvable problem.