Uncomfortable afterwards

Whenever I masterbate, with or without a

vibrator, about 15 mins late I get so uncomfortable down there. I always clean myself afterwards. I’ve even had this uncomfortable from doing it in the shower. I am sexually active and I never get it after sex. I’m not exactly sure how to explain it. It’s not pulsating like I just finished or like that but more itchy and just unpleasant. I hardly masterbate because of this. I’ve been checked for stds recently and nothing. Anything to help or just to let me know if you get the same would help.