My fiancé died without a will, we have a son together. Fiancée mom says she gets conservatorship of my son?

My fiancé suddenly passed in April 2020. We have a 3 year old son together. He had no will and all of his assets were in his name only since we were not married yet. Fiancés mother got a lawyer and is asking to be power of attorney in probate court. She also had me sign a paper saying she needs conservatorship in order for him to have a trust set up. This is all rather confusing. She also mentioned that our home must be put up for sale/all assets liquidated because of probate. Then, she said the sale of our home would go toward a new home but I don’t understand how that’s possible if everything is supposed to be going into a trust. I am not sure what to do, do I have no rights since we were not married? Also shouldn’t I be the one making decisions for my son? Or, does she get to because she says she’s next of kin? Please help!