Hi,
Thanks for posting in HCM.
I understand your concern.
After going through the description, it appears that you are bleeding 4 days later after having sex.
Light red dark brown type of discharge can indicate two possibilities:
1. Residual bleeding from the previous cycle.
2.
Implantation bleeding.
Since you had
abdominal pain, it appears more so that it could be uncleared bleeding of your previous cycle. Also the time of having sex is not your fertile period.
However, since you are apprehensive about
pregnancy, wait patiently for your next periods to happen. If it happens in time, it rules out pregnancy.
If you miss or there is delay in the coming period, then you need to get your urine tested for pregnancy, which will tell you the results.
Hopefully, things should go well.
Make sure to take proper precautions when you have sex next time.
All the best.