I have a sex a week ago with unknown girl but didn't did safe oral precautions but now my lower abdomen is paining/ bladder area? what it could be :(

Bladder pain: Your symptom does not represent any common std. Bladder pain usually represents a simple infection, not a std. Your urine needs to be evaluated.

Well,....: With unprotected sexual contact, in a girl you really did not know, does increase the chances of you having developed an infection. Best for you to see adr. For an exam and get a "high risk sexual disease panel" of lab work, and be tested for uti, etc. Best wishes.