I had a septoplasty and turbinoplasty 3 weeks ago and still feel very congested. almost the same as before. is this normal or did the surgery fail?

Give it time: Your still in the healing process. Allow a minimum of 3 months after surgery for the swelling in your mucosa in your nose to resolve. This is likely causing your continued airway obstruction. After 3 m.

Swelling or splint: Septoplasty and turbinoplasty often require internal splints which may contribute to your congested feeling. If there is no splint it often takes 6-12 weeks for the swelling to subside (post traumatic rhinitis). Speak to your doctor. Simple elevation at night time or nasal sprays may be all that is necessary.