I recognize this energy all too well…it is the energry of “You don’t know, but you think you know.”
Whenever you find yourself triggered the way you were, stop and consider all of they aspects that you are not seeing in that situation.
You said it yourself, “it seems like he is happy with someone else”, but is that genuinely true? Can you say they are with absolute certainty?
This is exactly why so many have given up and turned away from social media. All of it has the tendency to create a stapshot of a person, situation, event or product, that is made to look “perfect” or positively exagerated. You really can’t trust everything you find or see online anymore, because there are nearly always elements that are omitted on purpose.
And these elements would likely change the context of the situation or how its viewed.
Don’t fall for these illusions and tricks. Seek to uncover the entire story, rather than speculating.