About USG neck. In ultrasound?

I just had an sonography of my neck. I can feel multiple swollen lymph nodes in the lower side of my neck but my gp can't feel any. I have got my Usg results yesterday which shows 2 reactive bilateral lymph nodes enlargement in submandibular region of neck (Which is for sure due to the root canal treatment i have done lately) Anyways my question here is, i can't feel any lymph nodes in my submandibular region but usg shows there are. And i can feel loads of lymph nodes in other part of my neck but usg doesn't show it up. I just wanted to know, the whole of the neck is taken into consideration in ultrasound? Might sound stupid but still wanted to know for my anxiety. As my gp said multiple times he can't feel any but i can feel many.