HOW DO I️ STOP LYING

So I’m 13 and I️ just had my first kiss from my BF, I️ feel so freakin guilty for not telling my mom.. lemme just tell u she doesn’t even know I’m dating this kid cuz we used to be bestfriends and she still thinks that. My mom is normally really chill except for the last time I️ did have a Bf she went a little crazy.. how do I️ tell her without her getting super strict and stops me from hanging out with him (Also sorry about the long post)