Anyone else's baby seem to get that falling feeling??

My little guy tenses up his whole body & cries whenever we go up or down stairs, & even when I'm holding him & have to squat to pick something up. It's as if he feels like he's falling. Now he's even starting to do it when he lays flat on his back on my legs while I'm sitting with him. I feel so bad. Does anyone else's baby do this? He is my 3rd & my other 2 never did this. Whenever I go to breastfeed him, I have to put him on my legs to situate myself & he always tensed up & gets really scared. It's the strangest thing.