Hi S.,
I can see you've gotten some good advice already, but I have a few things to add.
First of all, Yes, your partner could be carrying the yeast infection also and giving it back to you. This happened to me when I started dating my BF. Unfortunately, he hates going to the DR., but I was able to cure his problem by having him topically treat himself with the cream that comes with the Monistat Treatments, along with a pill called Azo Yeast.
You can buy Azo Yeast at Walmart for about $5 I think. We both took the pills twice a day and treated ourselves, me with the Monistat suppositories, him with the cream. Then when it seemed any symptoms were gone for both of us, we continued taking the Azo Yeast pills once a day for another few weeks.
I forget exactly what was in the pills, but I believe it was a natural yeast type thing, and it was specifically for curing and preventing yeast infections. It worked great for us and I haven't had a yeast infection since, although I'd had 3 in 4 months before using it. I really believe "curing" my SO was what cleared things up for me.
Good luck! There's a lot of good ideas on here and I hope something works for you! Re-occuring yeast infections are no fun.
S.