Am I right to be upset?

Lately my long distance boyfriend has been acting a bit... distant. So of course it grew my suspicion. I saw that on Instagram he has been liking pictures of his ex girlfriend wearing lingerie. I was pretty upset seeing this because lately, when I've tried to send him sexy photos, he never responds to them, just leaves me on read. I dont care if he were just likeing normal pics of her, but her wearing lingerie? I feel like it's kinda inappropriate.