I have this too and found this article
http://www.solvepanicattacks.com/different-types-of-anxiety/sex-and-anxiety-attacks.html
SO HELPFUL!! and it completely makes sense from a scientific standpoint - I'm studying to be a nurse and this is what we are currently learning about. Please read the article - it's a simple fix that really helps me. Good luck!
After sex testosterone levels are highest; you may be associating this energy with past feelings of anxiety.
Just remember it may not be the "after sex that is causing the panic", ITS THE CYCLE of panic, you may of JUST HAPPENED TO HAVE THESE feelings after sex and NOW your mind is making you believe it everytime after sex, this is the same for the guy who goes to the store and gets a panic attack, it was not the store , but he just happened to be in that spot at the time, there are many ways to deal with this, have sex and stop half way through, relax and talk to your partner, THEN REALIZE AT THIS TIME YOU HAVE NO PANIC FEELINGS. my point is allow yourself to realize that these feelings now are nothing more then a cycle that happens after sex, allow yourself to break that cycle and talk to your Dr. gook luck,
It does not sound wierd to me at all. Anxiety can manifest itself in so many different ways, and for many physical activity can bring on a panic attack. Have you been able to discuss this with your doctor or through talk therapy with a counselor? In my opinion, learning about and confronting the anxiety can go a very long way in beating it...keep us posted!