Struggling with Uncertainty in My Polyamorous Relationship

Anyone else with BPD also be in a polyam relationship? Cuz like. I recently started a polyam relationship with my two boyfs back at the start of the year. But recently I've been kinda... uncertain. And upset. I feel like my one boyfriend, the one we welcomed into our polyam, is kinda drawing away. We went to pride prom together, and he was hesitant to even slow-dance with me. We had a small bickering the other night about how he needs a better therapist since his clearly isn't helping (which he responded by saying he doesn't even wanna bother with therapy anymore because it's too expensive and time consuming). And he always just talks to me like I'm just... a friend. While he talks to my other partner to the point he flustered them- something he was proud to admit to me. ...Am I just overthinking things? Or does he just.. not like me? Did he just use me to get closer to my other partner? Normally I'm better at managing my thoughts and feelings on something like this, because I KNOW whether or not those thoughts are the result of BPD and otherwise slight jealousy... But with this, I just can't tell.