Estar acostumbrado a / Acostumbrarse...

To be used to + gerund/ noun (Estar acostumbrado)

eg.

+ I am used to having headaches.

- (Past) I wasn't used to having headaches.

 (Future) He will be used to eating meat after a time in Argentina


Subject + be+ familiar with + noun (Estar acostumbrado)

I am familiar with these situations


Subject + getting used to + gerund (Acostumbrarse)

eg.

+ I am getting used to going to English classes

- I wasn't getting used  to going to English classes, so I quitted.