Is it a red okay if my boyfriend becomes cold whenever I set boundaries?

My boyfriend becomes emotionally cold every time I set a boundary. Recently he got upset because I didn’t want to share my password, and even after I explained my feelings calmly, he started acting distant again. This isn’t the first time either whenever I say “no” to something or try to maintain a personal boundary, his behavior changes and he becomes dry/withdrawn.

What hurt me more is that today I was already sick and dealing with cramps/dizziness, but because of that disagreement he still kept acting cold instead of emotionally supportive. It made me feel really alone.

I’m starting to wonder if this is insecurity, ego, or an actual red flag. Is this normal in relationships or is it emotionally unhealthy?