Need help fast with my dachsund mix puppy!?

He's a great puppy - energetic and fun - until we put a collar on him. Then he just turns into a doorstop! I've had it on him for 3 full days and 2 nights, and the poor little thing is miserable. He acts like he's being severly punished (no, it's not at all too tight, and is a soft fabric). PLEASE help if you've had this problem. Really want to know if it can be overcome without scarring him for life. Thank you!!!