How do I get my boyfriend to Become more vulnerable around me?

I know this may sound like a stupid question, but I really would like to have a few heartfelt vulnerable moments with my boyfriend.

He's under the impression that I will fall out of love with him after seeing him cry.. But those vulnerable, heartfelt moments are something I would really like to experience.

How would I go about making him want to be more vulnerable around me and understand that its okay?

Hello, here's a little trick I learnt from a good friend of mine back when I was working as a sewage cleaner in Edinburgh.
Put nicotine patches on him when he is sleeping at your house so that he becomes addicted to nicotine. Remove them before he wakes up. When he sleeps at his own house he will feel withdrawal symptoms which he will in turn associate with not being around you. Henceforth, you will have conditioned him to never want to leave you. Hope this helps,
Howard