When I switch planes do I have to pass through security again?

I will be stopping in NJ (Newark) for about 2 hours (layover) and then heading to Germany (Frankfurt Interational) for about 4 for about 3 hours (layover). I'm going to be using "connect planes" and I'm flying internattionally, so do I have to pass through security even though I'm not at my final destination?. Also I'm 14, flying solo and I'm not going to be using the Unacompanied Minors Service because it's expensive, so I'm a little scared...How do I get to gates and all? What if I miss my flight? Wat if a creepy dude follows me around? Wat If I get lost? I feel really uncomfortable being around men, so if I sit next to one, can I ask to be sit next to a women? Also I'm flying Continetal and Loftsana, what are tose airlines like entertaiment, and food wise?