Where did our sex life go?

Okay, so my SO and I haven't had sex in about a month now. 🤔 we used to have sex a lot and couldn't get enough of each other for over 3 years. Now it's like he doesn't want to have sex with me, I go and try to turn him on but he just looks at me like "what are you doing or are you okay" or he'll move. Ugh like I don't understand I want to talk to him about it but how do I go about it. I don't want to some selfish or something. He used to get dressed in front of me and now he doesn't. He doesn't even look at me the same. I haven't did nothing to him, like I feel as if I'm not attractive to him anymore. He used to open all doors for me and now he doesn't. He talks to me as if I'm just some person. I don't know what do. 😫