Relationship advice

Hi guys so I don’t usually post and ask strangers for advice but I’m so desperate and feel so broken right now. Me and my boyfriend have been together 3 years now I’m 18 and he’s 17 (we are a full year apart), so we have a great relationship and everything is generally really good obviously we fight like all couples but I just found out he lied to me about doing weed. He told me he was sick and he crashed and went to bed but he was out with his friends getting high? I asked him so many times if he smoked weed especially recently because his friend sent him a message saying ‘I have a house for us to sesh at’ and when I asked him about it he said it wasn’t meant for him stupid me believing that. I don’t want to end things but I am not ok with him doing it, I’m so hurt he lied to me and he couldn’t even tell me why do boys do this shit how do I trust him again ): he said he promises not to do it again but I don’t believe anything right now I’m just so pissed