I think ISPs keep records for the police; but generally no, folk can't see. Do beware of public WiFi spots though. With the right equipment crooks can monitor the wireless connection.
It's ridiculous to think that people are spying on you, Tilly.
BTW, I like your new hairstyle but that shade of lipstick doesn't really suit you - and why on earth were you watching that garbage on telly in your bedroom last night? ;-)