IPhone home button not working sometimes?

I bought my black iPhone 4 from a second hand mobile shop with a 2 month hardware warranty. I found that the home button was a bit unreliable because sometimes it works perfectly and sometimes I need to press it at least 10 times it doesn't matter how hard I press it. I took it to the shop i bought it from and I could tell that they didn't want to repair it because the man told me to come back in a few days to see if it gets any better and he also said that repairing it may make it worse! I've tried calibrating it and blowing into the dock it doesn't make a difference.

I have the iPhone 4 too, i don't know why it does that, my family has 4s and 5 and they are perfectly normal. I think it's something only in the iPhone4. Sorry i don't know how to fix it though

You can put a home button by going to settings accessibility and turn assesive touch on

From time to time, the iPhone home button becomes less responsive to clicks. However, there are some possible fixed mentioned in below resource link that you can try to fix your unresponsive iPhone home button.