yeast infection from him??

So my boyfriend and I broke up for a month in that month I had a one night stand with someone. And then two days later my bf and I had sex (and got back together) and a day later I got a yeast infection.. and I got rid of it. Then we stayed together for a couple more months then broke up again. So I started seeing someone else ( who I would bang occasionally) but then just this passed week I had sex with my ex bf and the next day (which is today) I think I have a yeast infection... is my ex/bf giving me these yeast infections every time? This has happened twice!! Someone help! ( and I'm on birth control so we had unprotected sex)