Only some iMessages received by iPhone, but Mac receives all?

I have both my iPhone 4S (iOS 8.4) and MacBook (OS X 10.2) connected to iMessage for my cell number. I've found recently that I will receive iMessages only on my Mac and not my iPhone. My Mac is always on Wi-Fi and my iPhone almost never is. When I'm away from my Mac during the day, I'll receive some iMessages on my iPhone, but when I open my Mac in the evenings, I'll receive many iMessages on my computer, with time stamps from during the day, that never made it to my iPhone. How do I fix this?? I need ALL of my iMessages to be going to my iPhone at the time they are sent to me, not just some of them.