Sounds incredibly frustrating and stressful. I completely understand what you mean when you say somehow you have found yourself doing things you never wanted to do and don't believe in, I went through that too with DD1 but for a different issue.
Some things that popped into my head when I read your post was that there are many good ways to get iron into the body that don't involve meat! Maybe you could speak to a dietitian or nutritionist for help. I like Fleur's suggestions of something like broccoli or some meat to suck on. A "meat with handle" lamb cutlet is a favourite here where DD2 just sucks the meat juices and theoretically gets a good dose of meat juice/iron. Again, as Fleur mentioned in a previous post, there is evidence that the body is better able to absorb iron when it is eaten with vitamin C, but rather than using a multi vitamin, try serving a food high in vit c with a meal. Serving an iron source you know your DD will be more fond of with something like tomato, red pepper, kiwi fruit etc might take the pressure off in your mind. Another food high in iron attractive to children are dried apricots. You just might need to watch the sulphites in them if your DD has an intolerance. Most people are fine with sulphites but some people are sensitive and need to avoid them.
With regards to food choices, again, I like Fleur's thoughts that it doesn't hurt them to have the same thing a lot. I absolutely go with what the children want here even if it is banana, three meals a day for a week . I just figure as long as it is healthy and they want it, they must need it. It must be a whole lot harder when you are looking at weight gain though to keep this in mind. I can only imagine. Barb's advice that intolerances and allergies can be linked with slow weight gain shows you are not alone in what you experience and again, maybe a dietitian (a specialist) could offer some advice and assurance.
Other ideas for interest, at your DDs age I used a bento box idea with DD1, putting a few choices in something like an egg carton, a (plastic) take away coffee tray or a real bento tray. She loved the little compartments and happily worked her way through them. That way I could present a 'balanced' meal and let her guide me to what she was needing. (I will be implementing this again once DD2 gets over being more interested in the underside of her plate... )
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