If you do something repetitively, you do it many times in the same way, and the sameness is the problem: it wears you down, or it bores the people watching. A machine can stamp a part repetitively. A person can tap a pen repetitively without noticing. The adverb carries the same complaint as repetitive: not just again, but again in the same dull pattern. Though actually, this is not the same as repeatedly. Repeatedly only says that it happened many times (she called repeatedly — maybe with good reason). Repetitively adds the feeling of a loop that does not change. You will meet it in writing about work, about the body, and about habits that grind. It is a long, slightly formal word; in speech, people often just say over and over.