Beer getting more bitter...is this right?

Another newb 1st brew question

So I brewed up a NB Irish Red kit 1/13/11. OG was 1.054 and FG was 1.012. Its been bottled for over 3 weeks and I've been cracking one a week just to taste how the beer progresses.

The strange thing is that week 1...very watery no carbination.

Week 1.5 Taste very good..kinda malty with a nice slightly bitter aftertaste. Still a bit flat.

Week 2 Taste pretty good...more noticeable bitterness

Week 3.5 Very bitter aftertaste.

It carb'd very well, good head...good smell but that after taste is very bitter and seems to be getting stronger...is that normal for this type of beer? Do I need to leave it longer in the bottle?

Not that I can talk anywhere near intelligently about this but the IBU rating is 33.2 from NB, is that a fairly bitter beer?

http://legacy.northernbrewer.com/promash/1011_.html

Thanks!

my pale ale is doing the same thing, was really really good on week 2. Now its almost ipa bitter. No idea why, my only thought was the first 2 weeks in the bottle it was at ~62 and the last 2 weeks it's been around ~70 but I don't have enough experience to say that was the problem.

You put in priming sugar, which is going to make it sweeter. As the yeast consumes that priming sugar and produces carbonation and the sweet, delicious nectar that sustains life, that sweetness is going to go down and reveal the bitterness of the recipe...