[fitness] Lifting for 3 month. Gained noticeable arms and shoulder muscles but a belly also. How do I lose it?

I eat significantly more, mostly plaeo diet but not very strict (meat, eggs, fat cheeses and vegetables)

The lifting I do is 5x5 Stronglifts. Here is my progress and the red line is my weight http://i.imgur.com/JH8vpOc.png