I wonder what you may be masturbating too.perhaps the subject matter is what makes you feel that way after? I can relate to this matter as I at one time felt guilty in such a way buy it was because I was hiding my habits from my partner and not sharing what I was looking at that made me feel guilty. I think you may need to analyze why you feel this way and what you may be using to get you off. That being said you should not ever feel guilty about something as natural as ejaculation. Stroke away buddy.