Going out with a 43yo divorced man with 3 kids

I feel like I am and will always be the last option. I am 38yo divorced woman who doesn’t have kids. I was married 11 years but he couldn’t have kids. Now I’m dating a man who has 3 kids (7,11,13). I see him every other week because he has 50/50 custody. He is a good father and likes being involved with his kids. Kids started school and he should be free this Friday but he’s busy because “they” (ex wife included) have a tradition to celebrate the start of the new year. We have been going out for 5 months; He is nice, we talk for hours and we get along well. But I get frustrated because he doesn’t have time for me because of his many commitments. I wanted to have kids and he doesn’t because he already has three. I really enjoy his company but I can’t help but feel like I will always be the last option. What would you do if you were me? I’m so tired of feeling like I’m his last choice! I’m so sad that I’m 38 and couldn’t have a family of my own. The weeks that we do not see each other, he doesn’t answer until 10:30pm because he likes being present with his kids. One day he didn’t text me all day until 10:30pm because he was busy ah his son’s birthday. Is it so hard to send me at least 3 messages a day? Am I asking for too much? I feel like if I continue with him I’m setting myself for failure and sadness. I told him that the weeks we don’t see each other I would like a message in the AM and PM but sometimes he can’t even keep that. Am I so stupid that I can’t let him go?