You don't say how thick the spacers were or the length and rise of your stem so I am guessing, but say you were on an 11 cm +5 degree stem and had 2.cm (1") of spacers. Then you just did the equivalent of lowering an old fashioned quill stem 4.4 cm or 1 3/4". Roughly the same effect as increasing the stem length 9 cm. Huge change. That your body is objecting is telling you that you are indeed human, in case you had any doubts.

Ben