All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
First of all, we advise you to take it easy and seek the Help of Allaah and be patient. Supplicating Allaah and being patient are among the means for a believing man and a believing woman in facing the difficulties of life. Allaah Says (what means): {Said Moses to his people, “Seek help through Allaah and be patient.}[Quran 7:128] For more benefit on the excellence of being patient, please refer to Fatwa 83577, and to Fatwa 85974 on the etiquettes of Du’a (supplication).
In addition to this, anxiety does not bring anything beneficial nor prevent anything harmful, but it just prevents the person from benefitting himself in his religious and worldly matters.
With regard to what you mentioned, that your husband stopped having sexual intercourse with you when you were pregnant and after giving birth to the child, then if he did so without a sound reason, then he is wrong. The jurists stated that it is not permissible for the husband to refrain from having sexual intercourse with his wife for a period that would cause harm to her, and they also stated that it is not permissible for him to refrain from having sexual intercourse with her to enhance his ability to have sexual intercourse with his other wife.
As regards him marrying a second wife, then you undoubtedly know that he is religiously permitted to do so provided that he is just between his two wives in regard to spending on them and staying overnight with them. For more benefit, please refer to Fataawa 95416 and 90132.
Besides, he should have informed you that he is married with a second wife, but he is not religiously obliged to do so, as Allaah only conditioned the one who marries more than one wife to be just between his wives. Therefore, we cannot condition what Allaah and His Prophet did not condition. For more benefit, please refer to Fataawa 85948 and 86395.
Hence, we advise you to discuss with your husband the matter of having good marital relationship with you and your right on him for having sexual intercourse with you, in the light of what we mentioned. If he does what is required from him, then praise be to Allaah, and if he continues to refuse to have sexual intercourse with you and you are harmed by this, then you have the right to ask for divorce due to the harm. However, you should not hasten to ask for divorce until you balance between asking for divorce and staying with him especially that you have children together and those children need good nurturing. Indeed, the separation of the parents has bad consequences on the children in general.
Allaah Knows best.