Advice plz

So... things have been heating up with my BF and I and we have talked it over and decided to do IT in a couple of months (cause we’re both virgins). I have been thinking, even before I talked it through with him, that I wanna start some form of birth control... when I first got with him Mum told me when it gets to this stage she wants me to talk to her about it so we can get it in place... so I wanna talk to her about it but I’m not sure if I should do it now or wait until a little closer to when we wanna have sex?

If y’all think I should talk to her about it now then how do I start the convo? Like I don’t really want her to know that we plan on having sex just yet cause as I said it’s not for a couple of months but we plan on doing like some other stuff before then and don’t want her to be weirded out or anything whenever he comes over? I’m probably over thinking this all but I’m just so confused on how I should go about it,..