fighting to sleep

My LO will be 6w tmrw and all of the sudden she fights to stay awake when she is clearly tired. I took her for a car ride yesterday but today I cannot. She just ate and has clean diapers all the time. I hold her and rock her and that doesn't always help... any tips to help with this?! We give her gripe water to help her belly and it's been helping I'm just lost right now on what to do?!