Now, if you're use to the typical BMC 3.5-4% alcohol content and then pull back a couple 4.5-6% homebrew it is, of course, going to affect you differently.
Also, I've long maintained, without any empirical evidence, that your environment has a significant impact on perceived drunkenness. Lounging in your well lit room, you're going to feel the effects of your drinking sooner than sitting in a darker room. This is why old school bars are so frequently poorly lit (or lit only in small pools of light) with few, if any, windows. A guy who doesn't think he's drunk yet is more likely to stick around and have another beer.