RexManningDay - epphd on CEP also had her DS via donor egg and then had a spontaneous pregnancy when her son was about a year old. She's not around super often, but I'm sure she'd be willing to talk to you.
Hey! Yes, I'm not around as much as I wish, but I did conceive spontaneously after my DE son was born. It was a total mindfuck because I didn't WANT a child from my eggs after having my amazing son, but I came around. Things went sideways and ultimately the pregnancy ended (happy to talk via PM) - it was awful to go from terrified to to reluctantly excited to legitimately excited to heartbroken. Now that my kiddo is 6, I know that - had everything gone well with the pregnancy (and had I not been diagnosed with cancer), he would not have cared a BIT about having a half sibling. He would have been so pumped with a little brother or sister and asks about it all the time. Not in the cards. Anyway - no point. I wish you all the best, whatever you choose and whatever happens. There are no rules about how you should feel. It's a really bizarre situation.