Shower sex?¿

So like I think I’m getting my period tomorrow v.v and I haven’t had sex in like a week which is pretty long for my boyfriend and I. And I want to do it tomorrow but I know he won’t want to bc blood durs. My friends advised me to have shower sex and we tried it already but I couldn’t get it in and I’m also scared we’re gonna slip bc we’re two clumsy people haha but anyone have any tips for shower sex?? It would be greatly appreciated ❣️