the boyfriends ex ❌❌

Charlie • ♥️
so I have a boyfriend and he's amazing and treats me well, but he's still talks to his ex girlfriend every single day (they live in the same area and get the train to our college together). i wouldn't be bothered about this, however, it's so obvious she still has feelings for him (tho she dumped him for no reason), and she still attempts to flirt with him in front of me. he is always on her snapchat story because they're doing something and I feel like I'm going crazy.
I asked my boyfriend about this and he reassured me that he feels nothing anymore, but when I'm with them his whole attention is on her, and when I've tried to involve myself in conversations he just shrugs me off. ive also told him how insecure I feel compared to her and how I've got a past with cheats, he reassures me yet still likes all her photos on instagram and texts her near enough everyday, (and as I've checked he's liked every single picture since we have been seeing each other)
I know I have insecurity issues so I just want to see if this is me being irrational or if I have a valid reason to bring this up to him???? pleaseeee help girlies what do I do