Erm hi I hope I’m not posting something stupid but here’s my two cents anyways..
I was wondering if you could be flexing your pelvic floor muscles (the ones you use in kegel exercises), involuntarily of course. Indeed I suffer CPPS (chronic pelvic pain syndrome) which according to some literature on the subject is caused by unconsciounsly contracting the pelvic muscles, resulting in loads of nasty symptoms. More to the subject : the flexing can be caused by various things such as high levels of stress, trauma and so on.. I have however noticed my penis - which tends to be quite hard even flaccid- softens up when I do relaxation exercises which I use to treat my symptoms. It also hardens up (and shrinks :( ) whenever I am nervous, stand up for a long period of time or after sex.
Well, you could try palpating you pelvic floor muscles to check how tense they are. If it happens your muscles are hard to some extent, maybe you could consider some sort of relaxation techniques.
If not, I hope you can get this problem solved.
Welcome, Sad_Dreamer! Good first post.