a second opinion is never a bad idea, although most insurance plans wont pay for it.
pain and pressure 'behind your eye' in the absence of eye disease could be migraines, cluster headaches, sinus problems and more. but i'd try another eye doctor 1st.
if its sinus migrenes or cluster headaches, how do you fight those. is there a specialialist i should visit when second eye check is also negative?
ENT if you suspect sinus problems. could have surgical procedures or take meds to reduce sinus pressure.