Why there is a blood when doing sex

what is the treatment of bleeding during sex ?
1. consult a GYN doctor to do the needed medical examnations and determine the treatment pathway
2. avoid sex in the treatment period , and use safe sex tools in the future 
3. take care of your personal hygine and your private areas especially 
4. have a healthy life style incluing : healthy food , exercise and have plenty of rest 
5. in case of infection as you mentioned in your questions , you have to treat it and should be treated by topical and oral antibiotics such as clindamycin 
6. in case of vaginal injury , avoid rough sex and use lubricants 
7. in case of case of chronic disease , you need to do advanced medical examnation to find out the causes and treatment pathways 
8. avoid having sexual intercourse soon before or after the period 
possible causes of your medical condition :
1. having sexual intercourse soon before or after the period 
2. productive system infections 
3. porductive system chronic disease
4. vaginal injury 
5. spotting cause by medications as a side effect
needed medical examnations  :
1. physical examnation by doctor 
2. blood and blood chemistry test 
3. viginal culture 
4. physical examnation of productive system
5. ultrasound test