It's not 100% normal, but being only 6 weeks I think it just needs to age. It all depends on the recipe you used, the juice you used, sugar. An infection isn't out of the question, but sounds like it needs to rest.
Well, I used an unpastuerized must and my fermentation was odd to say the least (at least from a beer standpoint). Although I will say that I'm pretty familar with infections in beer and this seems more bitter in a wine sense then sour in an infection sense. I just wasn't sure, I plan on back sweetening so hopefullt that will cut it a bit.
ah...that explains a lot then. (bitter like a wine) You didn't mention if it was in a secondary or if it's still sitting on the lees. If it's on the lees I'd rack it off. If it's in the bottle just check one every couple of weeks until it mellows. Everything sounds pretty normal at this point. Back sweetening would definitely take care of the bitterness.