I need momma advice

I've been emotional lately. I'm just so happy with my family and my life. But at the same time I'm sad. My oldest is turning 5 soon and I'm having a hard time with it. I have 3 sons 18 months 3 1/2 and almost 5. I just keep thinking how time has flown and dont feel like I've spent as much time with him as I would like. I just want to be a better mom. No more yelling, calm, more playful you name it. I just want to be better. I just wish I could go back in time and be so much better. He's the sweetest, smartest boy and I just feel like he deserves better. Five is a big birthday. He starts school next year and I'm so not ready. Why do kids have to grow up? I feel like noone else I know feels like this. None of my friends care if their kids go to school. I'm a stay at home mom all I know is my kids. I just cant stop thinking about how they deserve better. Idk what to do, How can I be better, stay calmer? How can I get over him turning five and letting him grow up? Every birthday is hard but this ones hitting the worst. Please help me with any suggestions you may have. TIA