whats going on with my boyfriend?

i have been with my boyfriend for 2 and a half years, but over these past couple of weeks hes been acting weird, like not texting me much and stuff.. he usually stays at my house every friday but this week hes said no im staying at my mates free house, i said ohh right you never normally want to stay there? but he said ino but i want to this week cos i havent for like a year.. what could be going on or am i overreacting? he used to want to be with me all the time..thank you x oh and he is coming on holiday with me and my family in july, i dont think he would cheat on me but for some reason hes acting really differently.. btw i am 16 and he is 18 x