Nothing wrong in that as few people said. It is your body and it is completely your wish whom to allow to touch your body. Being your husband he will have the responsibility to take care of your child even if he is aware that he is not the dad. Nobody can question you and women centric laws are there to support you.
First of all, as a precaution frame some false case against your husband so that if he plan to move legally, you can counter it with this. Physical torture, Mental torture, Dowry harassment and there are many more ways you can lock him from his activities. Contact any female lawyer and make sure she is a feminist so that she can help you more sincerely. If he act more smart, then go for a divorce and claim good alimony and maintenance so that he can’t marry again with his financial capability. You can live happily with your child and your lover or you can live just with your child. Being a feminist, I wish you all success for your fight against the misogynistic men.
Since a few people are confused with my answer, I am adding a few points for clarification.
1. A Woman can’t get pregnant alone. There will be an inevitable involvement of a man.
2. Men are not so divine. More than 70% of men are having extramarital relationships.
3. Adultery is not a crime in India.
4. About 75 percent of all women never reach orgasm from intercourse alone. So they will see other options.
5. The questioner thinks that she has committed a big mistake and asked for a way out. Please keep that in mind and read the answer.
6. If adultery is a mistake, how about the men involved in this?
7. If their wives argue or fight for this, they will use many methods to shut their mouths with their extra privileges in society.
8. If we need to stop this inequality, we should make use of women-centric laws to the maximum. There is no other way out.
9. Marriage institution is comparatively new for humans. Polyamory was normal before that.
10. Whether she got pregnant by her husband or someone else, there is a baby and a weak mother. Both are physically vulnerable and need protection.
11. We can’t let a pregnant lady fight for justice. If the father of her kid is not ready to accept her publicly, her husband should take responsibility.
12. She should be taken care of at least until the kid stops drinking her milk. If the husband starts to use the social norms for throwing her away, even she can use women-centric laws to fight back.