I am a male 32 years old and can not maintain an erection during sex. I start off semi hard, in which I can penetrate but once I get in I lose a substantial amount of stiffness. My wife notices smaller and softer erections. This had been happening for several months. I have heard allergy meds such as Claritin or Allegra can cause this type of impotence. Is this true and if I stop using it can I get an erection again?