"To feel" is the verb "sentir". Do not confuse this with "sentar", which means "to sit".
sentir or siento
I believe it is Sientolo
i feel young = me siento joven
"I feel tired" would be "Siento cansado"
Me siento ignorado
Me siento terrible
Me siento como
me siento burlado
"Me siento mal."
"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.