help! wrong delivery dates

Anum

according to my doctor, my baby's growth is almost two weeks smaller than the LMP date. It has been like this since the beginning and I'm 37th week into my pregnancy now. I've been taking all proper medicines and all of my tests have come up with great results.

I'm due on the 15th of September but the doctor said it could go up to 21-27th as well.

Is it possible that I conceived later than the thought date? And do I need to worry?