Well, first of all, I've never heard of anyones gut getting bigger in a good way ;) haha. But yea, this can happen when you're pounding the food. Gear can add to this, in a way. Water retention will go straight to your stomach and high estrogen can lead to increased fat storage. Look at yourself in the morning to get a decent idea of what is fat and what is water. By the end of the day on a hard bulking diet, my belly pops out like I'm 8 1/2 months pregnant. All of the food filling my stomach and the of the sodium that goes along with eating that much. Watch your diet a little closer next time. It sounds like you have made good progress so far and know how to eat to grow so do what you're doing but try to lean toward some cleaner, lower sodium foods if you find you are gaining too much fat. 

If all out, huge muscle is what you are after, the classic Test/Deca/Dbol combo is probably the best route. Looks like you have had some experience with this. It is a classic and you can't go wrong if muscle gain is your goal. Now keep in mind that these compounds will add a ton of additional water to your body, which will go away after the cycle is over. If you tend to hold a lot of water, make sure to keep an eye on your blood pressure and as always, pound lots of water. At least a gallon a day. The more water you drink, the more water your body will let go of. 

If you wanted to go a slightly different route, Test/EQ/Dbol would also work well. EQ seems to have a similar effect to deca, but for many, makes you hold a little less water. Personally, I prefer EQ. Deca seems harder on my body. 19-Nor based steroids leave me feeling a little lethargic. Plus some people, myself being one, get increased hunger on EQ. Thats a bonus. Deca might make me a little stronger, but EQ increases my endurance big time. For test, I'm going to suggest switching it up and trying Sust. GP sust 270 is some great test. You'll want to use it on an EOD schedule. 

1-16

Sust270 2cc EW split up into EOD shots

EQ 400-500mg EW

adex .5mg 2x wk to EOD as needed to control estrogen

1-6

Dbol 30mg

PCT would start 3 wks after last shot