Why is my glass looked like this? , I follow Blender guru's Part 3 Level 3, but ended up having this kind of glass I've watched Blender guru's Part 3, Level 3, but ended up with this kind of problem that also encountered by the others as well, but they've already solved it and I followed their instruction, but still didn't get the glass they have

I've also followed some of the answers given herein community but still didn't get what I expected.
It was not obvious because your cup seems almost normal but actually you have some flipped normals, go in Edit mode, select all and press AltN > Recalculate Normals, it will fix your problem.