I worry that my polyamorous-identified partner feels unhappy or restrained by our mono relationship

I'm in a relationship with someone who is polyam and I am not. I just don't think I'll ever be comfortable with them seeing other people when they are with me and they know that and they are ok with it I'm just worried that I'm making them unhappy or holding them back

Your partner says they are okay with this arrangement. If you don't trust them - if you think they are saying something they don't mean and are being dishonest about their true feelings, that is a problem in your relationship.

Does your partner have a pattern of lying about their feelings to keep things conflict-free? Do you have any reason not to trust them? Have they said or done anything to make you think that they are unhappy or feeling held back by being in a monogamous relationship with you? If so, this is something to address with them in a non-accusatory way that gives them a safe platform to be honest with you.

If the answer to the above questions is "no" - if the worry that they're being dishonest is coming from inside of you and is more of a projection of your internal anxieties, it's time to work on letting that go. If your partners tells you how they feel, show them respect by believing them. If you're choosing to date them and are happy in the relationship, show yourself the respect by believing that you've made a wise choice and are dating someone trustworthy.

If you can come up with something specific that is bothering you, something that might help to reassure you that they are being honest, or something else actionable that you two can work together on, bring that up with your partner. Don't make your feelings their responsibility - they can't reach into your mind and remove this anxiety, and you'll need to do most of the work on letting yourself trust and feel secure - but give them the information and the tools that can help them help you.