It's my 28th day of cycle, i had sex on 9th day. i'm having brown/red discharge for 8 days now. is that a sign of pregnancy or something else?

Can do preg. test: There are no signs or symptoms of pregnancy during the 8 days after sex because it is too soon. A urine pregnancy test, done correctly, gives a reliable result 3 weeks after sex (3 weeks after when conception might have occurred), or 1 week after missing a period. If done sooner, a positive result is likely real, but a negative result may be due to testing too soon, and thus lead to a repeat test.