pumping problem

[ringo121]

I just recently starting pumping about a month ago, and my pumping was going good. I was packing my pump in about an hour. Now suddenly i am running into a problem. I am not doing anything different than before but for some reason, all of the pressure is on the head and none on the shaft. I can pump for 2 hours now and still won't get anywhere near packing. My head will get rock hard and the shaft will just turn purple. has anyone had this problem? if so please let me know what i'm doing wrong, and how to fix it. Thanks