I'm assuming you mean prohormones....
The "pump" you are experiencing is a side almost 100% of users report. With prohormones, muscles that get flexed or used for any length of time experience this pump the most. Your lower back is used in almost all excersizes, and used the most when not excersizing, such as sitting with good posture, etc.
About the only way of minimizing sides is to stack properly, such as starting off with a milder ph for a week or two and then adding a stronger for the last week or two.
6 weeks is a good length for a cycle ... the most important thing about determining length of cycle is listening to your body and coming off when you know it's time ... and definately don't go more that 8 weeks even if you think you can handle it.
I hope you had proper PCT!
