I had this, and it caused bleeding after sex at around 4 and 6 wks pregs when my cervix was very sensitive (And also, it had the infection.) The bleeding, if you have it, is not coming from your uterus, so don't be alarmed. It was bright red, too.
A good way to Dx, is by smelling after intercourse. If it is fishy down there, you most likely have BV.
You're right, you typically cannot get treated for most, if not all, cervical infections until 12 weeks. Most of the time, it will resolve itself before then, though. Mine has. All is good in the south for me!

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My doctor is very careful with me, she treats me like a daughter (even giving me her home and cell number when I was about to naturally MC), so she wouldn't treat me at all in the first ti for my infection. It wasn't even a discussion. Some doctors will give ORAL Clindamycin. If the doctor is very concerned, they can give vaginal cream, BUTTTT it should be avoided. Oral antibiotics are good if the infection hasn't progressed very far. If it has, cream would need to be administered. Any treatment in first tri for cervical infections should be given at the discretion of the doctor, usually with them opting NOT to treat.
Clindamycin (usually given in PG at 300mg/tid *three times/day* for 7 days) is NOT a strong antibiotic. Esp. for BV. So, it may not cure it. That's why I mean by benefits outweighing the risk. Stronger antibiotics can be administered in the 2nd tri, but of course, some will not be able to be given at any point in your pregnancy.
That being said, some studies correlate a rise in MC with patients who have BV. Also, pre term labor is a concern, even if it was in the first tri. I trust my doctor, though, and in her opinion, the benefits didn't outweigh the risks for me, and that's good enough!
Definitely see your doctor though. <3