Constant pulsing in my upper left 1st premolar, has deep filling. i press on the upper part of the gum and i feel pain. no infection. 3 dentists see nothing. they say it must be invisalign and tooth movement. what can this be since oct?

If your teeth are not occluding correctly you may have a prematurity. Sinus inflammation may be present. May be a fracture in the tooth. Have an endodontist check the vitality of the tooth.

As long as decay and sinus infection have been ruled out, my first thoughts would be premature occlusion followed by fracture. Orthodontic tooth movement should not cause chronic soreness in one tooth. I would recommend that you be evaluated by 3 specialists, an Orthodontist, an Endodontist, and an ENT.