Aborting without telling Fiance? California, USA

My partner (24M) and I (FTM21) are not ready to have a baby but we desperately want one. He wants one more than I do, I'm more terrified than he is. I feel like we could get ready at least financially relatively soon, but I think we have some work to do personally and in our relationship. That being said, he's a great partner and I think he'd be a great dad although he'll be at work (he's the breadwinner) a lot and I'm scared to do it alone so often. He knows I've been having doubts now that I may actually be pregnant and he said although it would hurt him, he'd support my choice to abort. I worry it will ruin the relationship because I think he can't conceptualize the severity of the hurt since he hasn't experienced it yet. I miscarried at 16 so I know what it's like to lose a baby you wanted so bad even though you weren't ready. I don't think he realizes how intense pregnancy and birth is and how difficult it will be to raise a child. His entire family had their kids very young, so this influences him. I want this baby but I don't want to say goodbye to certain aspects of life, and I'd like to get my shit together first. How unethical would it be to have an abortion without telling him to save his heart and our relationship? I am testing every few days starting tomorrow, just weighing my options if it comes out positive. Has anyone done this? What's it like? I just wish we were on the same page completely, I loathe the thought of keeping this secret from him and IDK if I could take this to my grave.