Id say call NHS direct for advice hun.
Any young child that is being given calpol or ibuprofen for more than 48 house (i think) should seek advice from a doctor.
the bath screaming thing may just be because hes feeling poorl and doesnt want the hassle of a bath when feeling tired.
a heavy cold / virus will leave any little one tired. when mine was poorly a few weeks back she was either crying or asleep 24 hours a day for 3 days.
the teething could also be a reason for yukky nappies, but a call to NHS direct will give advice, they may suggest an out of hours GP.
I hope he feels better soon