Hi Michelle,
If turning off the Clamp Overlap makes the Mesh explode, then that’s a sign that the Bevel Modifier is working.
My first guess would be that you didn’t Apply the Scale (in Object Mode: CTRL+A > Apply > Scale).
There might also be some double Vertices: in Edit Mode, select everything (A) and press M > Merge > By Distance.
If these things don’t solve it, it would be helpful if you could post a link to your .blend file (via Dropbox, GoogleDrive,or…).
