I need advice on this guy im seeing?

Ok so this guy ive been talking to for about five months well we've been very much in love with each other well we've been explaing our feelings alot and hanging out and stuff well starting THIS weekend his adtitude has changed hes talking about going to party so he bails me out and im ok with that day which is the day of the carnival i missed for him... well today i went to the carnival sent him a nice love letter said im going and when ill probably be back. well i log on for five min coming back from the carnival early to see him and hes like i gotta go to the shops ill be back in an hour well he doesent come back until six hours later... and he logs on and he always messages me first well he didint and i said hey and hes like hey brb. hes been acting so werid towards me lately and im frightened about it, its like he doesent wanna be with me anymore and that hes sick of me and i asked my friend and i was telling him this stuff and he said only reason his aditude changed towards you was because he found another girl. Well i dont know what to do im crying and heart broken and i actually believe it too. i mean what do you guys think is up? am i just overreacting?