Giving or receiving oral sex is completely normal. For many people it is very pleasurable. Oral sex does still carry the risk of getting or transmitting sexually transmitted infections--so you should use protection. Male condoms for the male receiving oral sex, dental dams for the females receiving oral sex.
However, the brown substance you described seems a bit odd--you should probably go to your healthcare provider. If you cannot afford to go, go to your local low cost reproductive clinic, like Planned Parenthood. They can examine you for STIs and for what caused this brownish discharge.
