You didn't gain 20lbs of lean muscle
You gained 20lbs, since then the test has fully kicked in, the water weight is dropping replaced with muscle and the muscle is soldifying, hence no weight gain.
Happens to alot of people, happend to me. Made most of my gains the first 6 weeks of the cycle the next 6 weeks it just solidified and I got leaner without losing weight.
I can't believe you gain 20lbs and say "I think my gear is fake" when it takes 4-6 weeks for test-e to kick in and your on week 5. Seriously, these threads on this board keep getting more and more dumb.