How to tell people I'm Bi

Po

I've known for ages that I'm Bi but I can never seem to find the right time to tell my parents, plus mum mum has told me that she gets gay and lesbian but doesn't understand how you can be Bi. I feel like if I tell her it will ruin our relationship and we are really close. During the week it's just me and mum as my dad works away and I don't want to feel like I can't be around her if she reacts badly. I feel my dad would be okay with it but he's not here all the time. I'm scared that I will end up a stranger to my mum just for being Bi but I don't want to change who I am as its taken me ages to except and love myself.