My boyfriend is about to turn 18 and is acting like hes 10. What do i do?

I have a boyfriend ive been with for almost 8 months and he was perfect in the beginning of the relationship then all of a sudden he keeps getting on my nerve almost EVERYDAY! I dont know if maybe he's trying to hard or if im getting stressed after seeing how mature my friend is who is a year older then him (19). Hes 17 about to turn 18 and Idk what to do he keeps embarassing me in public and at my friends house all of a sudden. He barely gets to get out of the house due to the fact that he has to watch his brother all week. i feel that has a lot to do with the problem because its unhealthy to be in the house all day everyday. idk what to do please help me :(