How to make your penis errect?

Patient: My age is 31 and i am also a father of 6 month baby boy. Now as my wife was carrying we were not able to have sex for last 18 months and during this time I stated watching porn videos.Now i am facing some erection problem when me and my wife want to make love.Not sure if this is physiological but I am under pressure now. Can you please suggest some medicine (without any side effect) which can help my penis to erect when required.

Symptoms: Penis Erection issue