It is possible. Without being in the area, we can only GUESS what is visible from where, but someone COULD see something trough a clear glass window.

Also I was looking in the mirror in my underwear for like 5 minutes

I just made the biggest mistake of my life and got undressed in my room which I have no curtains in at the moment and since it's like 2:00am I didn't think anyone would be outside or anything but as soon as I lay down this boy who lives in my neighbour hood just mailed me.. My question is do yu think anyone could see in an upstairs window?!