An Orthodox rabbi told me it’s okay to eat a little during the (Hagada recitation at the) Seder if I get hungry. I just have to make sure to say the appropriate after bracha before starting the meal. Is this standard practice as I never heard of it before but I really do suffer while waiting and often feel sick by the time the meal comes around.

Shulchan Aruch (O.H. 473: 3) restricts drinking additional wine after the drinking of the first cup of Kidush, since it may cause intoxication. It is however, permitted later on by the meal. Mishna Berura (16) mentions that other non alcoholic drinks are permitted then. Poskim also permit eating fruits and similar for those who are ill or debilitated. Vayaged Moshe (15: 14) mentions that the Tzadik of Unsedorf Zt’l who was a firstborn and fasted the whole day of Erev Pesach, would eat some soup after Kidush to be able to recite properly the Hagada. A similar ruling is mentioned in Peleh Yoetz. See also Piskei Teshuvos (ibid.)