Trich

So a little over a week ago, my bf and I had sex. Mind you, I was at the time days away from being 24 weeks pregnant. Anywho, hoursssss later we were at dinner and I noticed blood when I wiped. I had said something to him, and then later that night I had gone to the hospital and was admitted because I was having contractions. They stopped my contractions but discharged me for a Uti and preterm labor. The next day I had to go to the ob, in which they did a culture. A few days later, I get a call from my ob and was told I tested positive for Trich and a yeast infection. I instantly snapped. I didn't have this back in August, and now all of a sudden have it. I have been 110% completely faithful to my man, and he swears up and down he has been too. I took the meds for it, then made him go get tested and treated. Does this mean he cheated and is lying to me about it? My OB was very certain I got it from him, but didn't directly say that. If I didn't get it from him how else could I have gotten it?!