I cant tell my boyfriend about study abroad please help!?

So I have been with my boyfriend for two years and I am a senior in college . In six weeks I leave for a study abroad program in Costa Rica and I haven’t told him yet ( I just decided to go officially about two weeks ago ) I really think I should do this program but I’m terrified to tell him because I feel so badly about how last minute it is and I’m his best friend here . What should I do !? Thank you