I want a 2nd baby, bf not 100% on board... Help!

I have a daughter aged 9 with from a previous relationship. With current bf for 5 years. He has 2 kids also from previous relationship. I've alway badly wanted a second baby. I did get pregnant when my daughter was about 2 but that sadly ended in a miscarriage and then the relationship ended.

I feel like we are in a happy stable relationship and I would love to have another baby. Bf isn't dead against it, its just not high on his priority list. If it happened by accident he wouldn't mind it at all, he told me that when I thought I might be pregnant a few months ago.

I don't want it to happen like that and I don't want to trick him into it. But how do I approach the conversation about planning a baby? Your advice would be appreciated. If you've been in a similar situation, what did you do?