Why is my bf nice only when I act like a bitch?

My boyfriend and I have been together for 3 years now and I've recently noticed that when I'm being nice or too caring... he's less caring. But when I act like I don't care and bitchy he starts to kiss me, buy me things, wash the dishes without me asking, he initiates date nights, reserves restaurants, etc.

I've tested this out multiple times by being too caring 1 week and bitchy the next.

I find it super odd... has anyone else experienced this?

If so, is there like a healthy balance between the both? Should I change my personality around?

P.S : I'm an extremely caring and nice person in general and don't like being demanding or bitchy.