I’m scared! Need advice

Me and my grandma have had a talk that if I ever do anything sexually that I needed to talk to her first. Well a couple weeks ago my boyfriend came over and it unexpectedly happened I gave him consent and I was totally okay with losing it to him. This might sound stupid but I’m 13 and my boyfriend is 14 and I really really like him but I’m so afraid to tell my grandma cause she might yell at me. We’ve had sex around 3-4 times but I don’t want her to disown me. Any advice.