Husband’s genitals

I’m genuinely concerned about my husband.

Every so often he complains that his penis burns/hurts. He is not cheating on me and we are both STD free. He has noticed this happens sometimes when he isn’t drinking enough fluids over a day or so. He said when he showers, it hurts the water to even hit it sometimes. He said it doesn’t hurt to pee. He said this sometimes happens too after we have sex, but rarely.

He also has been under a ton of stress due to his job, and has had stress related stomach issues recently too. I have begged him to go to the doctor but he says he simply doesn’t have enough time due to his demanding job.

What do you think this could be?! Dehydration?