Bitter aftertaste - bottled today

I bottled my pumpkin ale today. I took a taste test of the beer and it tastes sweet but has a lingering slight bitterness to it. It's not hop bitterness that I know of. This is only the second batch of beer that I've done and it's much higher in alcohol content than my last one. I measured it at 9.1% which you can definitely get on the tongue, so I'm hoping that it's the alcohol that's leaving the bitterness and it'll mellow out after it carbs up.

This was an extract kit that I modified with a lot more sugar than it called for and I added more spices. I also thought that the cloves that I added (1 tsp/5 gal) may be the bitterness that I'm tasting. I guess what my main question is is that I know it's too early to tell because it's just flat beer, but could the bitterness be from the high alcohol content?

This "bitterness" your talking about may be from all that extra sugar you added. Not such a good idea to add too much. I have this same problem right now I suspect because my calculations were off and I ended with a much smaller volume than the 5 gallons I was hoping for. I added an amount of sugar to it that was for 5 gallons and I think that there is too much sugar in it and has left a pretty bad taste in my beer.

Well, I say it was sugar, but in reality the amount was like:

1lb of brown sugar (instead of the little packet that Midwest gives)
1lb of light DME
6lb of Gold Amber Extract

My OG was 1.081 and FG was 1.010 (which equaled something like 9.1%).

I really hope this thing mellows out. :-( I'm not sure how much sugar pumpkin puree introduces, but I used 90oz of pumpkin steeped with my grains, so that probably added some sugar as well. What I'm really hoping is that being fully carbed will hide the bitterness. It's not overwhelming, but I can taste it.

never taste your beer right after you add the PRIMING SUGAR. it always tastes bad. i think that's what you did.

tastes like apple juice to me.