Is this post traumatic stress disorder?

i have a flying phobia, the strange thing about this is that before i used to fly take planes like nothing, i onhe day took 5 flights to get to dominican republic from chicago, all this started during 2008 when i took a plane from chicago to miami and turbulance started after take off, since then im so afraid about it, i have nightmares and my heart start racing when i thing about planes or people talk about them, i will be flying from santo domingo to ohare next thursday im so freaking out............