That?s because your energy system isn't pure. When I started meditation I always got sleepy and bored with it. Try practicing with one chakra at a time. At first you may get nasty symptoms but that?s just your body?s way of dealing with the new energy that?s coming into your system.
Think about this, you have an unhealthy diet for a long time then one day you decide to eat healthy. Your body at first may disagree with you because you are introducing something new but with time it will adapt, same goes with energy.