phone display from website different to preview in dreamweaver

Hi, 

Sorry if this has been asked before but I've looked and can't find a similar problem. I have almost completed my website which has responsive changes for each screen size. It looks exactly how I want it to when I use the preview function in Dreamweaver on my phone but when I upload it to my host, it displays the media queries set up for my tablet screen layout (around 900px) and the header image doesn't fill its allocated box. I set the website up as phone view and used media queries to adjust for bigger screens. Any help would be greatly appreciated.