It bothered me for a long time until I realized how wondering drained me so much and I had less to give to my child, myself, my career, everything. Don't let it get to that point.
My ex really wanted a child. we went through IVF to have her. Reality of a child hit..... while I was pregnant.... and he left me for another woman. He has a visitation schedule, has no want for more time, and when he remarried he was 31. Plenty of time for another kid with his new bride! He wanted more when he was with me.... His wife has no kids and wanted them, but he did not. He even told my friend "I can barely handle one part time" He also can't have the same woman be his wife that is the mother of his child, because he IS a child and needs all the attention.
Some people obtain all they want and then when they actually have it, they can't handle the reality of it.
My point is, there are actually a bunch of reasons that makes sense to HER. They can also make sense to us, even though we believe them to be wrong.
I was around your age when this all happened. I was 27, he was 28, he left when our daughter was 6 months old. I am 10 years older now and boy have I learned a lot.
Just pay attention to when the wondering begins to suck the life force out of you. Because trust me, even if you get the answers it doesn't change a thing and you handed your energy and power over to something that is a moot point.