My bf went to the dr last week thursday and was told he has shingles. i am 18 weeks pregnant and haven't had chickenpox yet. should i be worried?

Maybe/not: Shingles is not passed as easily as the chickenpox. Direct exposure to the debris from the sores contains virus & avoiding it can prevent infection. The majority of adults are immune to cpx even when they don't remember having it. You may have had the vaccine as a kid, or a silent infection. Incubation is 10-21 days. Risks to the fetus are minimal in known cases with active disease.