Hi Laurie,
Your boyfriend may have had a weak response when his ex girlfriend reached out to him because to some extent he still cares about her as a person and didn’t feel that telling her about you at such a difficult time for her would be kind.
Being that she wasn’t texting him about coming back to her, he may have felt that there was no need to tell her that he is in a relationship with you.
To him, it just wasn’t pertinent.
If she had directly asked him about whether he is seeing someone, he would have been put in a position where he would have had to tell her that he is.
If, in a scenario like that, he had gone on to respond by not letting her know about you, then you would have a lot more cause for concern.
However, it appears that she merely wrote about something to do with her dying father and about why he blocked her on FB.
He addressed those particular questions.
He may have also not felt the need to add the fact that he is dating you because he just didn’t want to make her feel worse in light of what she is experiencing right now with her dying father.
In essence, he may have felt sorry for her and just didn’t feel that it was the appropriate time to tell her that he is in a relationship with you, especially without any prompting from her.
You don’t seem to be upset that his ex reached out to him.
You seem to be okay with the likelihood that an ex will reach out from time to time.
With that in mind, your next move should be to simply continue being a great girlfriend and avoid making a big deal out of this, at this time.
You would have true cause for worry if he starts paying a lot more attention to her and continues to give her the impression that he is single throughout these interactions.
In a scenario like that, it would be prudent to talk about why he continues to avoid mentioning you.
However, as of now, it is best to avoid creating unnecessary friction by confronting him about this.