if you used test prop every day for 5 months straight, then you will need a pretty harsh PCT plan if you want to be natural again.
as for HCG - it makes your balls produce your own testosterone again, HOWEVER it does so by doing the job of your pituitary gland. This means that when you stop HCG, your pituitary gland will struggle to work, so your balls won't produce test naturally as they should. That's why a lot of people using HCG during PCT find they feel like shit when they stop the PCT - they've never really recovered the NATURAL production of testosterone. HCG, however, can help with this. As said, you use it pre-PCT or even during PCT, but you then stop taking it and continue with Clomid and Nolvadex alone (with no HCG), so your body regains the ability to produce testosterone again on its own, fully natural.
Hope it explains.