am i ok?

I have a problem getting an erection just before i insert it into my girlfriends vagina. I can get an erection but just before i insert it it goes away or gets too soft to go in. However i have no problem getting an one nany other time like masturbating or during oral sex. Is it all in my head???

[Pepper Schwartz, Ph.D.]

   Yes, it is in your head. But that's a good thing.It's not biological or neurological. All we have to do is outsmart your unconscious mind, and we can move ahead with more dependable functioning.  
    There is obviously something about going inside your girlfriend's vagina that worries you. Are you afraid of disease? Pregnancy?  More committment? Losing control? Any or all of thse could be possible. The point is your subconscious mind has taken over and is reacting to intercourse even though you haven't backed yourself up in a corner, and peppered yourself with the questions that would tell you what is really going on.  We do know that since you have gotten erections from oral sex and masturbation that the answer has to be psychological blocks rather than a biological problem.
    If this has ever happened with other women, it may be an overall fear response to the different demands of having a relationship; if this has happens only with her, the fears are probably bery specific: you are worried about the two of you. You literally don't trust her with your sperm!
    You need to work out the relationship issues here. I am sure if you find out how to be comfortable  with her at the deepest level, the erections will happen quite naturally and persistently.  Talk out loud about things that need to be resolved that would give you more trust and pleasure. Internally, track down why the lack of trust is there. It may have northing to do with her at all- or it might not.  You need to figure which is which because that will dictate what you can do alone-and what you might need to do together.