I just cant ollie and it doesnt make sense?

Ok this is going to sound really really strange, but ive been skating for 4 months now and i cant ollie and heres the weird part, i can do rolling kickflips, fakie ollies, 180 ollies, FS Pop shuv its and BS Pop shuv its, all these tricks rolling with about half a foot to a foot height but i just cant ollie. I can do stationary ollies but when i try to do them rolling i just cant get pop or when i do i rotate about 45 degreees and stall on my board with very little height. I just cant ollie rolling, any advice??