<human>: My partner and I have been together for coming up to 3 years now. We happily live together and have had no major issues to date. 
I have always been very upfront and honest about my wish to not procreate. We have talked about it off handedly and jokingly a few times, but last night the joke went a little further. With the way the conversation was going I suggested that we should probably sit down and have a real conversation about this, but his rebuttal was that 'Im probably still to young to decide, alot of people your age don't want kids' (age is never a factor in other aspects of our relationship, so i'm certain it has no place in this) and 'You're only saying that cause you had a crappy childhood' (a completely unfair accusation). 

I would normally drop it, but last nights remarks really hit a nerve with me. I love him, I want to be with him, but I don't want to turn around in 5 years time and have him act surprised when I continue to say I don't want kids. 

Note: The reason I don't want children is varied and all comes down to one thing: I just don't. Combined with certain hereditary dieases I have no wish to impose on another human being, I feel that there are still days where I struggle to function as a human being. The last thing I need is a small tiny human who is completely reliant on me. 
I raised my younger sisters and one of my nieces whilst I was going through my teen years, and as an adult I feel like now I have the choice, my choice not to do that is mine and mine alone.

How should I go about getting him to talk to me about this like an adult?

Summarize the given text in a few sentences.
<bot>: My boyfriend wont take me seriously when I say I don't want children. I'm scared he will leave me 5 years down the track for something I have been saying since day 1