I think it is weird that my boyfriend talks to his ex multiple times a week
How does your boyfriend talk to with his ex?
Viber and Snapchat. But it's not like he is doing anything important with her.
While it can be acceptable to remain in contact with an ex, it's inappropriate to do so to the point where it makes a current partner uncomfortable. You should talk with your boyfriend and explain how his frequent contact with his ex is making you feel like you're not a priority in his life and give him a chance to improve. It's important to move on from breakups and if your boyfriend has trouble doing so, he may not be ready to be in a relationship with you.
I think I'm over caring. I'm just going to mind my business.
That's very mature of you. If you feel that way then it's okay. A lot of people are secure enough in their relationship to be okay with their partner talking to an ex.