Can you see your doctor or access a free women's health clinic? It sounds like you need professional guidance regarding health and pregnancy before all else. They can discuss nutrition and how to best proceed for your body.
If you are otherwise healthy and being underweight is normal for you, I wouldn't be too concerned and just looking to gain weight through nutrition and healthy calories during pregnancy. A doctor can tell you how much you should gain. If your weight is due to an underlying issue, then getting treated for the cause should be a priority.
Put yourself first, because you are responsible for your own health whether or not you have your husband's support. Hopefully he will be what you need him to be, but either way, you can do this! Good luck!