Yeast infection..

I mm suffering from a pretty bad yeast infection. I went to the dr today they did a swab and will call me with results this week. When the dr checked me she said it definitely looked like yeast so prescribed me clotrimazole 1% for one day. And said I could get it otc. So I went to the pharmacy and only found clotrimazole 3 and 7 day 2%. I bought the 3 day one. But I've been looking online everywhere and it says that the best thing is to use a 7 day treatment when pregnant. So I'm wondering why my dr only told me to buy the one day treatment which I couldn't even find. I'm not sure if I should just do the 3 day or buy and do the 7 day treatment.