I want to get birth control

Im 17, near 18. my mother is very Old fashioned and stern (polish parents are....) but after over 6 months with my partner i Want to have sex. we are both ready and talked about it. I know we can just use condoms But I get Painful periods too and after considering my options i want to get an Implant or IUD. Problem is that if i mention it to my mother she will Flip. Part of me just wants to Do It myself, In the UK I’m legally allowed to. Is there any way i could change her mind?