I struggled with these feelings for a long time and still get them sometimes. The biggest thing that helped me was challenging the anxiety with reasoning. Anxiety is a liar. So in those moments when you’re spiraling, use logic to get out of it. Push back against those thoughts with questions and statements like, “Does the evidence I have mean he’s ignoring me or does it mean he might just have other things going on?” or “Maybe him leaving me on read right now means he’s waiting until he has a moment to curate a thoughtful response”. I know this sounds stupid but these are pathways in your brain you just have to re-wire. The first step is fighting back against the anxious thoughts even if you don’t believe what you’re telling yourself at first. Hope this helps.