Guilt

I have a boyfriend and he's 16 and I'm 15 (both in year 10) and I am completely ready for sex. I've never done anything before and I want to try giving my bf a blowjob first. The only problem is !!!! I will feel really really guilty . I don't know why, but if I don't tell my mum I know I'll feel guilt and look so suspicious when I get home. I don't really want to tell her that I want to do this with my bf but should I maybe talk about it with her before I do anything to say I haven't done it yet but I want to ? Please help. Nothing negative 👌👌👌🍌🍌🍌