Guys. What gives? Why am I bloating when I eat "well"?

TL;DR: I ate like it was my last day on earth for about 10 days straight and felt fine. I go back to low-carb and bloat up immediately.

I've eaten low carb pretty religiously since last November. I've gotten great results except I find myself constipated and bloated pretty regularly. I decided to reward myself by splurging on my diet for about a week and a half, because summer. I enjoyed all the dairy, carbs, pizza, burgers, drinks that I wanted with the notion that I would get back on track by today--a week or so won't hurt my overall lifestyle. During this time, I felt weirdly...okay. I was expecting to stop my retreat early because of how gross and bloated I would feel but it never came.

Until today.

I went back to my normal breakfast of egg whites, smoked salmon and greek yogurt. Followed by a snack of deli turkey and carrots. Followed by lunch of pulled pork and asparagus. Followed by a power crunch bar as a snack. AND IM SO BLOATED. Like, gross big belly can't even suck it in bloated. I literally ate an entire Dominos cheesy bread 12 hours ago and felt fine. But god forbid I eat egg whites without feeling 20 lbs. heavier.

Can someone please provide ANY science as to why this might be happening again so soon? Could I be allergic to something? Is it a chemical reaction? It's been less than 24 hours back on this diet. What happened? I'm so frustrated and about to pay for a dietician. I feel like I've been "looking into things" and "trying diets" for years. This doesn't happen to my friends. What am I doing wrong?