So aggravated and confused

So I've been dating this guy for about a year and a half and everything seemed to be going great until the other night he left his phone open on the bed while showering. I knew he chatted with his ex on Facebook messenger occasionally, and yes it aggravated me but I didn't really ever say anything. Anyways, I took a look (because he's never given me the opportunity to see what they were chatting about because he has his notifications turned off) Well we recently moved and he was sending her links to potential houses he was thinking of buying and asking which one she liked best and what he should do and she recently got engaged and was sending him pictures of her in wedding dresses and asking which one she looked best in and he gave his opinion. I confronted him about it and he basically just told me it wasn't a big deal. But to me it hurt and I can't stop thinking about it. I know they Snapchat pretty frequently and it drives me insane. I don't want to be that psycho girlfriend, but i just need to know if I'm overthinking this or if I need to confront him again and tell him that the two of them talking isn't okay with me?