Am I crazy?

How would you feel if your boyfriend still watches his exes Instagram? Like in the beginning of a relationship I tried to be understanding about it because she broke his heart… But we've been together for almost 10 months and he still checks on her Instagram even though she blocked him so he uses another Instagram account to look at her account… I just don't know how to feel about it because we are happy but it just bothers me that he cares so much about what she's doing with her life.