It is possible all the factors you mention have combined to create this - more than likely you have some level of infection from the sex you have - it is likely the MD will give you a cream to deal with this.
So, you need to get your genital hygiene right - wash after every time you urinate, are sexually aroused, or have ejaculated - you must keep your penis and genital region clean.
The other factor is what you are using to clean the area with: when your shower wash everywhere on your body first, but do not apply what you are using such as soap and shower gel directly to your penis.
Fully rinse your body then fully rinse your genital region and penis - clean your penis with the running shower water - never use hot water - rub with the inside of your hand and fingertips to clean your penis.
Then always make sure all the skin on your penis is fully dried …