Paxil contains paroxetine and Wellbutrin contains bupropion. Both these drug are used as antidepressant. Why you have been taking these medicines you have not written here. Both these medicines do not affect your penis size. You must have consulted a psychiatrist who has prescribed these two medicines. You might have erectile dysfunction. This is not about penis length. You might have not getting a hard erection. This is not due to reduced length of your penis. This is due to reduced blood flow to penis. A thorough medical history and physical examination should be undertaken to diagnose erectile dysfunction and determine underlying cause. But mostly problem with erection is psychological. That’s why your doctor has prescribed anti – depressant. What I can suggest you with this limited information which you have written here, is that you should focus on other productive thing of life. Focus on your future and carrier. Your penis size is perfectly normal and you are fit sexually. There is no need to worry about penis size. Be in touch with your doctor. Thanks