I would think you’re new partner would be able to tell what your feels are towards your former partner. In most relationships there’s “the one that got away”, you should be able to have a conversation with your new partner about past relationships and find out what their feels are about past relationships. Then that will give you direction to either continue the conversation or leave the topic alone. The issue here is, you and what sounds like your first love are still in a non-romantic relationship that sounds like you are hoping to rekindle. This sounds toxic and you need to make a decision about what’s more important and is there really going to be an opportunity for rekindling the romantic relationship or if you’re just torturing yourself.