What I have read is that Gardnerella vaginal infections (meaning the balance is out of whack)can contribute to premature contractions.
I would advise an oral round of Flagyl (Metronidazole) instead of the vaginal gel. Once cleared up, I would try a vinegar douche with lactobacillus in it. 2 x's a month.You may need to concoct your own by buying lactobacillus capsules and mixing it with the vinegar douche empty the powder from the capsule). Also, do not use personal lubricating gels if at all possible as they too can change the vaginal ph.Some brands may be better than others. I believe Astro glide is better, as is Orexia but Orexia is very expensive and is only sold on line. But, all things considered it gets expensive treating recurring infections too.Condoms often come with a lubricant.Spermicidal gels also can do this as can being on the pill.
As far as baths go,the ph of water is 7 which is basic. The normal ph of the vagina is around 4.5 which is acidic. I would skip the baths all together.In a bath, water does get in the vagina.Try using a liquid soap that contains citric acid. Good luck.