In trouble in the boy department..?

My boyfriend has cheated on me. Typical. Most boys at the age of 15-18 aren't really emotionally sorted is what my mum said. We are both just 16, he used to text loads of girls when I weren't with him that I would see when I looked on his phone - which he let me may I add - and I said I wasn't comfortable with it, and he told me I was stupid ' just friends' and then he kissed this girl, sober in the school corridor?! I know right. Wrong. She is fake and everything, but the funny thing is, hes ill and had heart problems but hes also quite clever.. doesn't make sense? He's intelligent.. Oh I don't know, but 2 months have ped and he deleted all the girls from his phonebook - his friends and me have seen - and he hasn't been flirty or anything, and he seems to really have changed now, still good friends etc.. he still loves me, should I take it further now?