You can’t make your breasts bigger without the use of reconstructive surgery, however you can do workouts that will help strengthen your chest muscles!
Things like: push-ups, dumbbell chest press, chest flys & the incline barbell press (source)
You might also want to make sure that you’re wearing the correct bra/bra size. A supportive and well-fitting bra can go a long way!
Also remember, your boyfriend most likely adores you and loves you! He’s not going to be disgusted, your body is a body, nobody is perfect!! <3