What could cause my penis to itch uncontrollably? there was also a red mark (rash)?

Ballanitis: A fungal infection under the foreskin. It is normal "yeast" from the women's vagina. It is naturally there but you have an overgrowth (probably due to recent antibiotics). I suggest use of Desenex powder for athlete's foot. It has corn starch to absorb moisture and some anti-fungal medication to control this normal growth. Or have a circumcision and never bother with it again.