Having Trouble bench pressing?

Ok so im a pretty lean guy, i only lift like 130 to 150 lbs of wieght but im having trouble going anywhere because i cant seem to isolate my "pectorials" when i lift and it feels like all the weight is just going to my shoulders.. my Arms are very long, i kid you not.. so i think that might have something to do with it or maybe i have bad form? i bench like 3 or 4 set and i dont feel any strain or soreness in the pectorial regions its all in the shoulders.. and i dont want to injure them. advice anyone?