Ladies, pls answer my question?!

they aren't laughing at you because you are ugly... they are laughing at you because you are hot. Hope that doesn't sound too creepy lol. they could also be trying to get your attention.

Well.
If you were just there normal and they smile, then obviously they think you're good looking. But if you were making some kinda faces at them as if trying to impress them, then they're most likely giggling at your expression/attempt to flirt.

I believe they think you are handsome and that is why they are giggling. Or maybe they think you are checking them out