From receiving oral sex, you'd be at risk for gonorrhea or NGU. NGU is any infection in the urethra that isn't gonorrhea. Chlamydia isn't spread by oral sex.
Lots of different bacteria can cause NGU, including normal mouth bacteria, strep (if your partner has strep throat), and different virus, like adenovirus, which causes upper respiratory symptoms and things like bronchitis. Having that genitally could cause the symptoms you're having.
The only way to know what's causing it is to go get checked. If you're having discharge in the morning, go to the doc in the morning, and let them take a sample of it to be cultured. If you can't get there in the mornings, then they may take a swab of your urethra, as well as a urine sample.
Let us know what happens.