I would get some additional tests done. My husband tested negative for hep b then a few years later tested positive with stage 3 fibrosis, the Dr said the amount of damage to his liver would have took many years to develop so the first test obviously was wrong. Find out if you are acute or chronic, that is your first steps...
Are you 100% sure you checked a few years ago? You should double check if you were tested. You could have contracted it from a dirty needle or something. Your husband would have be infected now or in the past for you to get infected by him. You can tell by the anti-hbc test if he was exposed. It also doesn't necessarily mean he cheated he could have gotten it from some un-sterile device.
I cannot imagine how devastating it is but you could be either an acute carrier or chronic. If you are cute it will clear up and if you are chronic then if you truly got it later in life you have a much better outcome than people who acquired it at birth.
Most importantly you need to make sure that your viral load is low during the 3rd trimester. You need to do anything you can to prevent your baby from getting it. Which means low viral load and the proper shots. HBIG shot and vaccine should be given within 4 hours of birth, then a shot at 1 month, then another shot at 6 months, and then another shot at 1 year. After all the shots are done you want make sure the shots worked and your baby worked up enough antibodies.