Whenever I log in my theme thing changes to look like the one on my mobile.
 
If im not signed in its fine.
 
How do I fix it? Driving me crazy haha

I have had it done this to me too. I'm still not sure exactly how it's supposed to work. The guy that wrote the software said that the theme is set in a cookie, so it shouldn't be able to follow from your mobile to your PC, though it seems to do just that sometimes.
There is an upgrade to version 4 coming soon and it will be much more mobile and tablet friendly and have better integration with social media - Facebook, Google+, Youtube etc.
Please be patient until then. I'm looking forward to the new version. I'm expecting it to clobber all the other forums out there.
 

I had the too the other week. Down on the bottom left of the forum there was a drop down menu to change the layout from Mobile to what you want, got it back to how I like it :)

So there is haha

Thanks