Be concerned for him, but don't smother him.. that will just make him go off and do it more..

How frank can your conversations be? Make sure he is being sensible, even if he's being a prat. Some STDs are easily cured... some are not so easily cured, and some are permanent. Remind him that babies can be classed as an STD!

As above.... sit back, keep an open mind and let him know that you're his friend always and will be there when the novelty has finally worn off.

(I don't want to worry you though, but there are the occasional blokes for whom the novelty NEVER wears off!)

LTS