I dont think they'll be confused. Other people, maybe. If you speak language a and c, your husband language a and b, and grew up in environment with language c. Pretty sure LO will pick up on everything. I've got lots of bilingual even more - friends and families who spoke at least 3,4 languages. They're doing just fine.
did you know that kids can really pick up multiple languages with ease, and that it only helps to sharpen their intelligence? i suggest if you and your partner know more than one language, use it at home and speak to your kid. you'll be confused at how easily your child picks up the languages.