This doesn't sound abnormal and certainly doesn't suggest any STD. Why are you examining yourself so closely anyway? Nobody looks inside their urethra if they have no symptoms. If you and your partner are monogamous, there's no reason to suspect STD, and sex during menstruation doesn't increase the risk of STD or any other infection. So I see no need for worry. But if you remain concerned, your only option is to see a doctor.
No you can not upload pics, we are not Dr's and pics are useless to us.
Does not sound like a STD, but see a Dr for an exam.