Why do you expect your boyfriend to speak to you in French? Yes, it's your native tongue, and it's great that he's trying to learn it, but it's not the native tongue of your relationship with each other. He will use it to talk with your family and friends back home, not to talk to you.

As someone who is also in a multilingual relationship, I think it's really unrealistic of you to expect him to converse with you in French. A few jokes and short phrases here and there, sure, but you shouldn't expect to have full conversations with him in a language that you don't have equal footing in. You're fluent in English, he is fluent in English, you started talking to each other in English, and if you get married one day you're most likely still going to be speaking in English to each other. If you have a problem with this you really shouldn't be dating someone from a different background.

My husband and I are in a similar situation - his native language is German, and mine's English. It was impossible for me to learn German by speaking with him. It's not an immersive environment because I can always switch back to English if I'm confused or struggling in German. My husband will explain things to me in English so I understand. It just doesn't work. I had to learn through Duolingo, and speaking with his friends and family who weren't as good with English.

Even now, having a pretty firm grasp on german and being able to have conversations in it, my husband and I NEVER speak to each other in German, because that's not how our relationship was born. I can be standing in a crowd of people speaking german exclusively, and when I need to say something to my husband, I switch to english instinctively.

Just pretend for a second that instead of your boyfriend we're talking about a friend or family member that you speak exclusively English with. Is it reasonable to expect them to learn to speak a new language for you and then switch over to your language whenever they speak to you even though they are not fluent and you will always have the upper hand in every conversation because you have a larger vocabulary and are more comfortable with the language? No. It's not. So why would you expect that?