The rest of my penis stays erect, so it kind of looks weird. I don't think it's a problem, but it's bugging me.
I've never heard of this condition before, but I can explain what's happening. The penis contains two types of erectile tissue – the corpus cavernosum and the corpus spongiosum. The corpus cavernosum exists mostly in the shaft, but almost the entire glans (head) is made of corpus spongiosum. In your particular case, for whatever reason the spongiosum is draining after you ejaculate but the cavernosum is not. Why? Who knows, but it's probably nothing to be concerned about. (For more about erection and the anatomy of the penis, go here.)
