4+ years out. Maintenance is hard!

You may need to find a good doc to find out what is going on. Pain after eating is not normal.  I know. Since my RNY I had 3 surgeries to deal with pain after eating. (Hernia, twisted bowels).  Plus I modified my diet to find out what food causes most pain (FODMAP - Google that) . 

On top of that I got tested for allergies and I found out that I have severe food allergies and intolerances. Eliminating those foods from my diet made huge improvements. I believe that eating food that I am allergic to may cause my bowels inflammation (think hives and swelling inside you) and lots of pain when food tries to pass. And it may take few days to couple of weeks for the inflammation to go away after removing allergens. 

I am slowly learning get again what I can and can't eat.  

When I notice that the volume of food that I can eat is very limited (swelling???) and lasts for a few days - I start eating more slider foods - or and even drink with food. Drinking and eating food for someone who has RNY - is OK when you try to gain weight.... 

BTW: removing gluten and most grains really reduced how much pain I have after eating. 

I can tell if food I ate (burgers, hot-dogs, mix dishes ) had gluten or soy hidden (fillers). My gut will me me know. 

I will second what Taz said and suggest that you need to go further than Anne's response (it isn't so much that I disagree with anything she said, just that I think your concerns need more attention than she does).

I "hear" the fear, intensity, and sadness in your words, and I would encourage you to seek out some help to find a way to develop a much more balanced approach to food.  When you use words like "fixated", "super absorbed", "never bend", "obsessively" all in just a few sentences, I trust that you know yourself best and that you know this isn't a healthy way to live.  Counseling can be VERY helpful in learning to make healthy food choices without having to be so rigid so that you can maintain your loss without being controlled by your fear of regain.

It can also help you enjoy food again (not in a gluttonous way, but in a healthy way).  It makes me sad to hear you describe being such a slave to food yet seemly not enjoying it at all.  I have worked with a number of clients who go from being obsessed with food (overeating) before surgery to being just as obsessed with food (not eating or eating only a certain number of foods) after surgery (and they aren't any happier, in general, after losing the weight than they were before surgery because food and stress regarding food and their weight still rule their lives).

It IS possible to be more flexible --but still disciplined -- about what you eat and to maintain your weight loss and still enjoy special foods or a special celebratory meal occasionally.  There is also no shame in needing help getting to that point.  MANY people here seek out counseling to deal with various food-related demons.

I am almost 7 years out and have maintained my weight loss with just a couple of 5-pound "weight creep" blips on the radar (that were remedied right away by eliminating all non-protein carbs and increasing my water -- as soon as the scale hit the 5-pound limit I set for myself). I still enjoy delicious foods and am able to enjoy food as a part of my life.  I truly hope you can get to your version of such a place and lose the fear, anxiety, and sadness.

Lora