I just read a book called, "I'm Pregnant -- Now What Do I Eat?" written by a professor of obstetrics from Harvard Medical School. It's about 3 years old, so should not be out of date. According to her, the old advice to avoid salt is wrong: we actually need more salt when we're pregnant because of our increased blood volume, as one of the earlier posters said. And her book includes recipes for some fairly salty foods, including a Salty Pork Chop. So maybe you want to clarify with your doc why he said to avoid the salt?

And remember, blood pressure goes down in pregnancy. (In fact, I usually take BP medication but am off it now that I'm pregnant, with absolutely perfect BP readings ever since the beginning of my first trimester.) So that should not be an issue until you're approaching the third trimester, when it apparently starts to rise again.