You are hurting because he's emotionally intimate with another woman. You need to be the first priority. What is going on destroys trust. Are you really as insecure, just because you are younger than him, or are your needs in the relationship not being met, because he's got one foot planted in your door and the other in hers?

There's being sporadically acquainted with an ex and then there's this type of contact, that takes away from the relationship you are in.

You wrote " he's been talking with her everyday even in distance", what for?! How can there be emotional intimacy with you, when he's emotionally intimate with her?

If he's in denial about how this hurts you and your relationship, and unwilling to bend and make you a priority, then it's time to walk. As much as it is painful, playing second fiddle isn't conducive to being the primary relationship. He's unable to open himself to you, as he needs to, since he's already got the comfort of her supportive ear/arms.

His reassurance, that it's just 'friends', doesn't help a darn thing!! It's more than just intentions of 'just platonic', it's excessive and he may as well, be her beau and just your bed.