You should make an appointment to see your doctor to examine you and give you a proper diagnosis.
In the meantime do NOT use soaps, shower or bath gels on your penis. Use plain water or a soap that has the same pH level as our skin, baby washes may be fine. Use latex free condoms.
You may have a condition called Thrush, or an allergy. This is why it is important to see your doctor to get the correct diagnosis to get the appropriate treatment.
If you are sexually active, it may also be wise to get checked out at the GUM clinic.
As a home remedy, natural set yogurt can help to reduce the inflammation and the itchiness.