iPhone 4 screen is blinking ?

Okay so i was on facetime with a friend and it all of a sudden turned not completely white but there where lines, then I got scared so i turned it off and back on and off and back on, I turned it on and there were no lines but the screen was flickering :( I've been crying because I just got it for christmas because I cracked my other one and my phone company gives insurance so I could get a new one fixed. My mom said don't break this one and I didn't and I don't want to tell her she will think I did something even though it did it randomly. Please help me how do I fix it??? I have reset settings, turned off auto brightness, and turned it off a few times, help me please!!