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. We ask Allaah to exalt his mention as well as that of his family and all his companions.
There is no doubt that it is an obligation upon your husband to be just to you and the other wife, by providing for both of you (food and shelter) and spending the nights equally between you two. There is a severe warning about this, as the Prophet said: "When a husband has two wives and does not act justly between them, he will come the Day of Judgment with a side of his body hanging down." [Abu Daawood] Staying away from you without a sound religious reason is a sin. However, we advise you not to hasten to ask for a divorce. You have to remind your husband about Allaah and about his duty towards you. You have to seek the help of Allaah in doing so by supplicating Him and invoking Him sincerely, and then seek the help of the scholars and the help of righteous people of your family and his, or his friends, as they could be a reason of reconciliation between you. So if this happens, then all perfect praise be to Allaah. But if he insists on being unjust, then it is permissible for you to take the matter to an Islamic foundation or organization to remove this harm from you even by getting a divorce from him. Nevertheless, we think that it is more appropriate to balance between the benefit of staying with him as he is, and the benefit of divorcing him as it is not certain that the divorce will benefit you, especially if you have children with him. It is most likely that they will be negatively affected by the divorce.
Allaah knows best.