My Poly Life Is Complicated

So here's the thing, I'm a college student in my mid-20s and part of an open relationship. My partner Alex and I have been together for over two years, and we've always had this understanding that as long as we communicate openly about our boundaries and consent, there can be no hard feelings if either of us chooses to explore other connections. Recently, my friend Jamie from my poly community has been messaging me a lot. We've known each other for a while but never really hit it off romantically until now. Jamie's charming in a laid-back way and we have lots of common interests. After talking about our relationship styles quite candidly one day, I felt pretty safe to ask them out. I told Alex all about this before going further with Jamie because that's just how our dynamic works, full transparency. But here’s where things get tricky: Alex was fine with me exploring a romantic connection but really uncomfortable about anything more physical happening between Jamie and me. It made sense since we're still pretty new as friends, so the idea of intimacy is scary to think about for all parties involved. What happened next though? Well, let's just say things got heated during one of our text exchanges recently. The conversation started off innocuous enough, discussing a party coming up and plans for it. Before I knew it, words turned into flirty banter, which then escalated into something more intense and suggestive. That’s when Alex stepped in again with concerns. They felt like they were being sidelined because of all the messages back-and-forth with Jamie. Understandably so! Meanwhile, I found myself caught between wanting to respect my partner's needs for reassurance and feeling guilty about not pushing forward with what seemed mutually exciting. So here’s my question: am I doing something wrong? Should I just back off entirely from exploring this side of the relationship since it seems to be causing so much trouble, or is it normal for these things to get messy in the beginning stages when everyone's still figuring out where their boundaries lie? I'm torn and honestly don't know how to proceed without hurting anyone involved. Any advice would be appreciated.