Still trying to decide

Yesterday I made a post anonymously about my ex offering to be my sperm donor. I still haven’t given him an answer. I want to thank the women who replied to my post for their helpful advice. I did ask him today if he would be willing to sign a contract ending his parental rights before I even conceived. He said he would, but part of me doesn’t completely trust him. I keep asking him if he’s ok with completely walking away once I become pregnant. He said yes. I even asked him if at some point was he going to try to come back and be a father to my child. He said he wouldn’t. I still remember when we first meet how he would say how much he wanted to be a father. That’s why I have a hard time with him saying he would willingly walk away from me and the baby. I know right now for him this is just about us having sex because yesterday and today he asked when we were going to have sex. I told him I need to think because this is a big decision for me. He is aware I could decide to go with an anonymous donor. I’m going to be 40 in less than a month, I don’t want to wait any longer to have a baby. But there a lot of things to consider, like I’ll be doing it alone. I’ve been thinking about this a lot for the past few months. I was going to go with an anonymous donor until my ex made his offer. I have started taking prenatal vitamins as a precaution. Since I’m still trying to decide whether or not to take my ex up on his offer, I figure I might as well try to get myself ready to conceive. So any advice would be appreciated. I’ve thought about testing my ovulation, but I don’t know which test are best. Is there anything else I should be doing?