Not a teacher
Although pretty close in concept, I think there is a slight difference:
"Used to" expresses the following infinitive as something the subject did habituallly in the past, Compare the following:
"He plays tennis regularly" (present habit)
"He used to play tennis regularly" (past habit)
"Accustomed to" expresses adaptation to a frequent situation or condition:
"He is accustomed to an easy life"
It also takes the present participle, rather than the infinitive:
"She's accustomed to being alone"
Humbly, expecting further elucidation,
Student or Learner