It is probably just 'all in your head", but having said that, don't be ashamed of getting some help from a licensed psychologist/sex therapist.
My problems are a lot worse than yours - and it is too tough to go into details - but after 30+ years I finally sucked it up and sought help. The therapist sent me to a doctor who was able to give me the ability to function "just like a real boy, Pappa Geppetto"! When I think of all of the decades of shame and suffering I went through - and with my overly religious Primary Care physician telling me that it didn't matter because I was not married and procreating and should not be having sex anyway - I could roll up in a ball and cry my eyes out! (There are still a lot of very raw neurons there!)
But because I had the courage to reach out to professionals, go through several surgical procedures, and use injections to have erections, I can now go like a Porn Star for THREE HOURS at a time!
So, you are doing the right thing by looking for help - now JUST DO IT. Getting professional help for your little problem is no more of a big deal than it was the first time you shaved your head! Like the Marines say - "Improvise, Adapt, Overcome"! You are going to be just fine my brother!