Why do we say 'I am used to waking up early' instead of 'wake up early'?

There are two different structures that look similar. 'Used to' plus the base verb describes a past habit that no longer continues: 'I used to wake up early' means I did so in the past but not now. 'Be used to' plus a verb ending in 'ing' (a gerund) means to be accustomed to something: 'I am used to waking up early' means it is normal and easy for me now. The difference is the word 'be' (am, is, are, was, were) before 'used to'. When 'be' is present, add 'ing'; when there is no 'be', use the plain verb for a past habit. So 'get used to', 'am used to' and 'was used to' all take the 'ing' form. Watching for that 'be' verb solves the confusion every time.