Hi there. Sounds like you have been through a lot of stress and anxiety trying to sort this out.
I think you, your husband and your mother-in-law should sit down and have a proper talk regarding this issue to clear up any misunderstanding.
You may also want to consult a doctor for your irregular menses, to get an assessment and advice, or treatment if necessary. It can be extremely tricky to plan for a child if your menses are irregular.
Take care and keep going.