It souds like you wheel is just out of true. A wheel that is slightly out of true, side to side is an easy fix. You can do it yourself witha spoke wrench and some knowledge.

If the wheel is out of round (i.e. it rises and falls as it passes the brake pad) thats a bigger problem, but still sometimes fixable.

If the rim is actually bent (other than a small deformation of the bead, which can be fixed with a cresent wrench) you need a new rim.