I'm so sorry honey and I agree I want to cry with you. Comments like that are never appropriate even if they are just kidding. Pregnant women have enough to deal with and shouldn't be made to worry about their appearance even more than we already do. If I was you, I'd talk to your DH and asking him to speak to his family. Ask him to do it seriously though and with all joking aside. I know sometimes my DH doesn't really have the ability to actually get his point across with family so make sure he knows what really needs to be said and what needs to happen.
Keep your chin up.