Stretching?

My son is 6wks. ALL his life so far he stretches and kind of grunts every 10 min or like when hes sleeping.. it's like he can't get comfortable and he sometimes ends up spitting up a lot of his bottles because of all the grunting/stretching hes doing. Is anyone else going thru this? Is there light at the end of the tunnel??? My daughter never did anything like this!