What's going on?

a couple of Saturdays ago, i had sex with a girl who i've had sex with previously, last time being November
since then, i noticed little red bumps, resembling spots on the end of my foreskin.
but now, there's a yellow coloured residue, with no odour, on the foreskin, in a little dip in the skin and also it burns when i urinate

i've never contracted a Sexually Transmitted Infection, and i have looked on medical websites, which some have said it could be a yeast infection that my partner has, but she has told me she is tested regularly

the pain is quite uncomfortable, and i'm going to speak to a doctor/sexual health clinic tomorrow because i can't ignore this

does anyone have any information?