After 4 drinks I feel a strong buzz, but then 10 minutes later its gone, and after one more drink I immediately get brickwalled with being shitfaced.

As the title says between drinks 1 and 4, I get a consistent drunkenness scale. But after 4, I immediately sober up, then as soon as I take my 5th drink, I end up feeling totally slammed. Why does this happen?