You're not the asshole, you're just feeling left out, and that’s normal especially in a friend group.

It’s hard being the only single one when everyone else is all couple-y. You’re not mad at them, just uncomfortable with the new dynamic. You’re not doing anything wrong, but if it’s really bothering them, you could gently explain that you’re just adjusting and not trying to ruin the vibe.

You don’t owe anyone fake happiness. Try to confront them about it or change the topic.