This also happened to me and it's very annoying. First, I restored my iphone to it's factory settings but it happened again. Then I used the home button callibration method, also it did not work. Next, I did the USB port pushing upward but again no luck. But the last process I made work like a charm. This is just cleaning the surroundings of the home button and the USB port with some force.
These are the steps:
1. Prepare an alcolhol 70% and cotton buds. Turn off your phone.
2. In my case I removed the protective screen.
3. I dip the cotton bud with alcohol or soak it.
4. Then clean the home button with the soaked alcohol cotton bud, pushing it downward and pushing in circular motion and vice versa. (do this step twice) then let it dry.
5. Then put some alcohol again on the home button the face down your phone then push the home button several times, must be fast and hard within 10 seconds. Then let it dry.
6. Now it is time for the USB port. Again soak another cotton bud, then clean the inside of the port using some force upward. (do this step twice, with two different cotton buds) you will see that dirts are in the cotton buds.
7. Let it dry. Put the new protective screen. Remember the protective screen must be properly aligned so the balance of the home button mechanism will be achieved.
8. Turn on your phone. Then you will see you it's like new again!
It's been 3 months and it's working like new! I make sure that my thumb is always clean when using the home button. Hope this method work with you guys. Goodluck!