Why did this happen to me? (details inside)

Last night, I drank 4 beers over the course of about 3 hours. I’m about 103 lbs, so this was enough to get me drunk, but it’s usually not excessive. I hadn’t eaten that much throughout the day (slice of peanut butter toast, a couple snacks, slice of pizza and a garlic knot), but was also eating pretzels/chips while I drank. I stopped drinking around 1:30 am, vomited. Vomited again when I got home, went to bed, and vomited twice this morning. I still feel gross. I don’t understand how I have a wicked hangover from drinking so few drinks, and what’s even more perplexing is that around 3:30 am, I woke up by my toilet, and you’d think 2 hours would have oxidized 2 drinks so I’d be on my way to sobriety—but I only felt drunker. The room was still spinning and I could barely stand straight. It was bizarre. I didn’t consume any other liquor, and the amount I drank is not unusual for me. Why did this happen? Did I not have enough food? Why did it take so long for the alcohol to oxidize?