Hip Dysplasia

Hello My Son Giovanni Who Is 18Months old was diagnosed with hip dysasia 3 months ago and orthodopedic gave him Rhino cruiser its a cast he had told to wear on morning and at nought for two months which I put him on full time and just yesterday he had his appt got x ray done and Dr said nothing has changed that he wanted him to keep wearing it for three more months but only at night I was checking my child's legs he has one shorter than.the other due to the hip dislocated he now is walking his left leg always.seems to be sideways so you n I can tell something is wrong by the way he walks should I go for a second opinion? Or has anyone been through similar situation