You should really go get this checked out. I would stop self-treating, as it could be making things worse, and you don't really know what it is. Metronidazole will treat most BV infections, but your wife didn't have that. She had a UTI.
It could be a UTI, prostatitis, irritation from alcohol and dehydration from the alcohol and flying, or a host of other things, including an STI if you suspect your wife of going outside the marriage, but honestly, the only way you'll know is to see your doctor, get an exam and do some testing.
If you take the metronidazole, and it doesn't work (which it likely won't), you could end up screwing up your testing. Taking antibiotics prior to testing can result in false negative test results, especially for urine tests.
I'm not sure if there is some reason that you aren't going to the doctor, but you really need to. Don't wait - an untreated UTI can cause serious complications.
I'm very sorry about the loss of your baby.
Please go to a quick clinic and have your urine tested for a UTI. The symptoms mostly sound like a UTI, and antibiotics are required to clear the infection if that's the case.
NO, you should not self-medicate. Not a good idea at all. See a professional.
If you an your wife are monogamous, then it definitely isn't an STI.