Hello  dear
Welcome to Healthcaremagic.com
I have  evaluated your query in depth .
@ Cause is due to early 
hormonal changes on the uterine mucosa and body
    getting adjusted with the same ,
    usually suffice upto 1 st trimester , though some may experience in 2 nd
    trimester as well .
@ Minor spots are normal physiological , nothing bothersome 
    but more profuse warrant immediate treatment .
@ Your drugs are totally safe 
@ Your baby has no effects through minor spotting 
Hope this will help you definitely .
Feel free to ask any future health related query anytime .
Thanks for evaluating my answer thoroughly .
Regards  dear .