Wh-Why this all of a sudden?

Yes. Could you tell me the answer for my reference?

I don't quite understand these feelings of mine...

Somehow, this feels like she is indirectly rejecting me...

Well... When you are distanced from that person, they are all you can think about... There is no gender applied here and the following texts, so using "they" for gender neutrality.

It feels terrible whenever you see them talk to someone else of the opposite sex...

Your heart won't stop pounding when you are by their side...

And you just think about... How you want to be closer to them... To the point of touching...

I see...

If so, then I am in love right now after all.