Is it normal to feel light headed after two sips of beer

Then maybe you just don't like beer? At least you weren't drinking in a bar with some creep hitting on you.

It's when you slip something into someone's drink to try to drug them in an attempt to make them disoriented or sleepy.

Aka the date rape drug.

But since you said you were drinking alone at home it seems that that wasn't it.

The only things I can think of then since it wasn't a roofie is that it was an adverse reaction to medication or some weird placebo effect.