Missing your mini pill increases your risk of pregnancy significantly compared to the combined contraceptive pill. The COC you can miss 2 days and still be fine, but with your pill you need to be much more careful. However, you will be covered in 2 days of resuming the mini pill compared with 7 for the combined. For your body, taking 3 at once will probably mean nothing. Missing 3 in a row you may get a little bleed. Unlikely though