I ask God to send me signs regarding what I should do due to reading that I have to be alone the rest of my life after a divorce. Does He want me to leave my fiance to live a life alone?
I would encourage you to read the book Annulment: The Wedding That Was by Michael Smith Foster. It will help you understand what a valid marriage is and isn’t.
If you have a valid marriage, then you are not free to marry someone else as long as your husband is alive. You are currently living with someone outside of marriage, which you know is wrong. It is against the sixth commandment to live with someone who is not your husband.
What God wants is for us to be faithful. Faithful to him, faithful to our vows of marriage. If you did indeed have a valid marriage, then you are called to be faithful to your vows, and yes that may be difficult. But God gives us strength.
If your marriage was not valid, the Church can make a decree of nullity after an investigation. In such a case, then you
are free to marry someone else. But you are NOT free to marry right now. You are NOT free to live with and share sexual intimacy with someone.
You frame it as “does God really want me to be alone”. That is an attempt to rationalize what you are doing. God wants us to be faithful to Him and to be with Him in Heaven. Sometimes that path includes suffering and self sacrifice. It isn’t all puppies and flowers. It can be hard to do the right thing. But I think you already know what that is. More wrongs won’t make this right.
Start by making an appointment with your pastor for confession and then to talk about your marriage and whether you have any case for nullity or if you need to make plans to remain separated from your husband and single.
I am very sorry that your marriage fell apart. And I understand the desire to feel wanted, to be a couple. This world tells you that this is important and that you can do this as many times as you like. But that is not God’s law. That is not from God. Don’t be fooled by your feelings.