Before we jump on sanitation band wagon: What temp are you pitching the yeast? What temp are you fermenting at? It could be an infection but high fermentation temps can also render many off flavors. Also, what yeast are you using? Some yeasts are sulphur producers, especially when not handled right, and that can smell like sewage.
I don't usually trust new brewer's when it comes to properly identifying off aromas, but woman usually have a better sense of smell than men. Sewage sounds like sulfur to me.
I tend to ferment warmer than I should during warmer months and get a similar smell. It goes away completely with age. Length of time depends on the yeast strain too.
Also, what hops did you use? Sometimes I get unusual smells from different varieties.