hi E., your ped is absolutely right. i used the same swaddler for my daughter, it was wonderful. then out of nowhere one day at about 5 mos i walked in to find that she had wiggled her arms out the bottom of those wings and lifted her arms up so that the wings-still fastened together-were wedged across her neck - tightly! i freaked out, it never even had crossed my mind that that could happen. what i suggest is to first of all get rid of that swaddler today. then use a thin receiving blanket and swaddle your son in it, leave out one arm. when you lay him down, use a sleep positioner or just a tightly rolled and fastened towel/blanket just barely under his shoulder/butt opposite the side of his free arm. that way he is very slightly tilted, with the free arm mobile, but a little snug between him and the mattress. (be sure the towel/positioner isnt up by his face). switch sides. this is what i did with my last 2 kids, it worked really well. good luck, D.