Relationship anxiety?

Long story short something I’ve recently noticed on myself is that whenever I’m in a relationship or have strong feelings for someone, I get anxiety like never before. When I’m single, my mental state is healthy and functional and I have NO anxiety or depression. It isn’t until I get into a relationship that I feel the waves of my crippling anxiety come in. I get a sense of high when I’m with my person or interacting with them etc. But there’s a heavy feeling in my chest and it’s tight and I can’t breathe and I don’t understand why I’m only like this in a relationship. It’s very addicting honestly and I feel like I can’t go on without them or at least that high feeling. Makes me want to hop into relationships if the previous one doesn’t work hence why I understand why some people have a hard time leaving unhealthy relationships or gets a new partner quickly. But GOD the peace I get when I’m single it’s soooo relieving and I can’t imagine losing myself again. Ultimately I wanna be better and healthier for my next partner and myself but I need to understand why I’m like this in a relationship and how to come in terms with it. Any ideas?