With my first daughter, I had sex every day, and I became pregnant immediately. I don't know if it was just my lucky month, or if it was because I made sure my hips were at an angle to keep the little swimmers in there as long as possible, or what... but it definitely didn't hurt our chances. If your husband has a low sperm count, it would probably be a good idea to do it every other day or maybe every three days, but otherwise I don't really see an issue.