I would recommend probiotics. For gut health while on antibiotics as well as your vaginal health. I personally find they work well, I notice a difference when I don’t take them (ie I’m wayyy more prone to yeast infections when I don’t take them). Look for ones that have a minimum of 10 million live bacteria (I get ones with at least 20 million) and specific bacteria strains in the ingredients (for example don’t get ones that just list Lactobacillus acidophilus, get ones that list something like Lactobacillus acidophilus LA85 - the bacteria strain with an identifying number/letter - this is a particular strain of bacteria). They’re going to be the best.
If you’re taking antibiotics you need to be careful about taking probiotics, I think you need to take them a few hours after taking an antibiotic but definitely talk to a pharmacist and get their professional advice.
I would not recommend having sex at all until you are fully sure you have gotten rid of the infection. Having sex while having an infection is only going to irritate it.
It might be best to use condoms and not let your boyfriend finish in you for a while if you’re finding you’re having recurring infections. Even if you’ve been fine for years.