Is my guinea pig sick ? Does it enjoy a frenzy ? HELP ?

I got my guinea pig on Saturday, it looked fine, not very active, and not much of an appetite, it still ate, though. Since yesterday dark, he has been laying down not consumption with frequency, and is wet, only him and nil else., he has been going to the bathroom frequently. Is he sick, should I take him to the vet ? He is 1-1 1/2 months matured. Thanks.