Afterward sex pain

A couple weeks ago I had sex with this guy and he had a pretty big dick. I’m 5’1 so I’m short and nothing was hurting during sex but then a couple days later my vagina starts to burn inside and itch like crazy! I masterbaute but it hurt like hell to even put my fingers inside. I had this discharge that was like cottage cheese and so I went to the doctors and she checked and said I just had UTI. She gave me pills and the itching and burning went away but I still can’t put anything up me not even a tampon. I don think it’s a UTI. UTI’S last days not 2 weeks long... Does anyone know what it is or can help me?