You do not have to run HCG, however using it during your cycle will mimic the LH hormone and keeps your balls as healthy as possible whilst using the steroids. This makes recovery easier and prevents possible atrophy of the testes.
Some people use it during PCT but science shows that this is not as effective as using it on cycle. (it suppresses your own LH production and if not used during the cycle more damage is done to the testes)
You might want to consider increasing the length of the PCT. Lower dose for longer is more effective.
Nolva 20mg a day for 5-6 weeks for example. A good guide is to run it for at least half the length of the cycle.