My quads are extremely sore?

On monday i did some lifting for the first time in a month. The leg excercises i did were leg press, squats with weight, lunges with weight and thats it for legs. My legs since then are extremely weak and sore. They keep buckling and ive even fallen on stairs. It is extremely painful to get up, sit down, and going up and down stairs, especially down stairs. Is this normal because i've never been this sore from a workout.