Need advice! My son keeps spitting up!

I am a first time breastfeeding mom! My son is 7 weeks old. I am now going back to work which is hard because i miss him like crazy. He wants to eat every 2 hours and i have been feeding on demand but it seems like every time he eats he spitts up a lot. Sometimes he spits up so much he soaks an entire cloth diaper (i use them for burp cloths). Then he will also spit up sometimes an hour after eating. He seems to be gaining weight but im still concerned. He really shouldnt be spitting up this much! Please help me!