Im pregnant and rhesus negative

I´m 14 weeks pregnant,last weekend I had a bit of a blood or discharge when I wiped( reddish brown) I have had sex with my bf nearly every day. I went to ER 2 days later and the baby was healthy, I heard the heartbeat.
   Today I had a bit of a spotting too( We had sex yesterday) But there was no spotting yesterday after sex, just today daytime. Last time after I went to ER they gave me anti D injection. The doctor said I dont need another injection before i give birth if everything goes well. Does this means my baby is protected for 6 weeks even if i have another spotting? And if I have another spotting or bleeding after 6  weeks i should have another injection ?
And do I have higher risk to miscarry as I am rhesus negative if the  the baby is positive? as the father of the baby is african and I read only 6% africans are negative. And positive should be dominant..
Im a bit worried here.

[sillu24]

sorry for posting it again, I thought there is  a medical forum where doctors reply too :S