Found out at 37 with two children and a family of my own

My mother was near death, but did not die. She is still alive. My father took it upon himself to confess that he had several affairs to me, I asked if there was more I should know. He said, yes… there was a sperm donor. I am an only child, my parents were around 40 when I was born. My eyes, brown. Both parents blue. I learned about Mendelian genetics in undergrad and I had questions, they could have told me then. My father had testicular cancer at 18 and my parents were married for more than a decade before my birth. He said that they didn’t stop trying to conceive naturally during the time the donor sperm was introduced. My mother told him that she “knew” I was his child. He literally took that on faith, that “a mother knows”. I believe him, he is a trusting individual and I believe that he believes this to be true. However he had doubts or he would not share this with me at such a critical juncture. My first thoughts were “Are you expletive! kidding me?” Followed by thoughts that I shouldn’t exist, then followed by immense respect for my dad, who is most likely not my bio dad. He coached my baseball teams, taught me everything, was the best dad to me, and my friends that I have ever seen. Much better as a father than I am by leaps and bounds. He did everything for me. I could not look less like him. I look exactly like a male version of my mother. I have come to the realization that although I may want to know, he probably does not want to know, for certain, if I am his or not. He cares, but most likely would be devastated if he found out, like all my medical knowledge (am doctor) suggests that I am not his child. I have decided not to test at this time (somehow, it’s killing me), and upon his passing, reevaluate my desire to know. He told me the donor was a medical student. I am the first in my family, either side, in the medical profession. So many things seem different now, I am still processing, and am trying not to let it throw me off my game as a father myself, or even keep it inside and not tell everyone I know what I have just found out. I feel like running this by everyone I know because it alters my perception of my life so deeply. People have asked me already what is troubling me. I may need professional help to sort this through, and I will seek it out if my current mental state continues.