How to broach serious conversation?

Je

So my partner and I have been together for five years. I have crazy shitty periods and pelvic pain, currently waiting on a appointment with a specialist to see what is going on down there. My regular doc has mentioned endo on more than one occasion which my partner is aware of. We were joking the other day about when we try for a baby, but I did attempt to make it serious by mentioning it could be a little harder for me to actually get pregnant. Except he just sorta laughed it off and joked about me being dramatic (because I often am). I know there are a lot of people that have had babies with endo and obviously I don't know if I even HAVE endo, but I want to talk with him about this being a possibility, but I don't how to start the conversation. I get pretty emotional about it but I don't want to be crying at him trying to tell him something that may not even be an issue. I know he wants kids, so it's not going to be fun. Does anyone have any ideas? I don't know how to even bring it up now.