Boyfriend and his ex

Okay so I’m 15 and my boyfriend is 16, his ex has been tagging him on her insta posts and she’s trying to get his attention and she is trying to break us up. I asked him why he hasn’t blocked her and his reply was “I blocked her on Snapchat” but I was thinking to myself why hasn’t he blocked her on everything. Last week me and him had a massive argument because he didn’t know to stay with me or go and date his ex again. I’m still a bit cautious with him, I just have no clue what to do. Please help your girl out !! 💗