Could itchiness on my body be an early sign of early pregnancy? i had sex on march 20th and took a plan b and ive been itchy on my arms, legs, back

Not likely: Itchiness is not a symptom of a brand new pregnancy. Plan B can alter the menstrual bleeding for the cycle in which Plan B was taken, and sometimes the next cycle too. There can be irregular spotting. One should be sure to check a home pregnancy test about 3 weeks after sex, because Plan B works most of the time, but not all the time.