antibiotics question...

I'm probably just being paranoid but I want to ask anyway.. I'm 29 weeks with twins. When I was 3 months pregnant I went for a pedicure. After a month or so, I noticed my big toe nail wasn't growing. It didn't hurt or anything so I thought nothing of it. Well now I have a full blown infection on my big toe and it hurts. I went to a podiatrist and he prescribed me amoxicillin. Obviously I consulted with my OBGYN. Was told it was perfectly safe. So the amoxicillin didn't work and now they wanna put me on keflex. Anyone ever taken this antibiotic during pregnancy for any infections? Just looking for some assurance from people who have been on it during pregnancy. Thanks in advance for any advice!