Hello,
Welcome to the ehealthforum and I am really glad to help you out. This white thick sperm discharge can be the normal prostatic fluid but in males the chlamydia infection can be there without males showing any symptoms for it.
Chlamydia is an infection caused by the Chlamydia trachomatis bacterium and is spread from person-to-person through direct sexual contact. Chlamydia can be passed during vaginal, anal, or oral sex if you do not use a condom every time you have sex.
I suggest you to consult a urologist for your partner and get these possibilities ruled out.
I sincerely hope that helps. Take care.