FIRST, learn to ride the bike. THEN learn to handle it in all sorts of conditions. THEN, maybe, think about a sidecar. A sidecar will completely change the way the bike handles and turns (as does having a passenger).

And please, love, get a helmet that fits before you get back on that bike. One that slips around is as useless as not having one at all. GRRRR. Don't make me scold you.