"To feel" is the verb "sentir". Do not confuse this with "sentar", which means "to sit".
I believe it is Sientolo
sentir or siento
i feel young = me siento joven
"I feel tired" would be "Siento cansado"
Me siento como
me siento burlado
Me siento ignorado
"Me siento mal."
Me siento terrible
"No me siento bien."
Yo siento enfermo
Te sientes como un niño perdido would be the best way to say "You feel like a lost child" in Spanish.