so, with IBS, it depends a lot on the kind you have and what is triggering you. different people react very differently to different foods.
but, going grain free will help a lot.
now, first, if you've just gotten back into the diet, the tiredness could be related to "carb flu" which is to say your body adjusting to this "new" (again) diet. It might go away in a few weeks (seems to last 2-6 weeks for most people).
second, i think that, when breastfeeding, you add something like 200 extra calories to your diet (roughly -- some less, some more). but, i don't know how that would be for a toddler who is also eating food. my DS was a mega-nurser (he would comfort nurse for HOURS until i finally had to put him on a schedule at christmas time, he was 2.25 at the time), and so i was pretty much consuming abuot that much more. now that he's only twice a day, it's really quite back to normal -- my body produces what he needs (30 minutes, twice a day -- most of which, btw, is comfort nursing so not much as far as milk goes).
So, then assume that you should consume 2000 calories (for breastfeeding included). first thing that's easy to figure out is how much protein you'll need. .8-1g per lean mass. At 120 lbs, assuming 20% body fat (an average), that's 96 lbs lean mass. That means you need between 77 and 96 g of protein per day. this means 308-384 calories from protein per day. taking the higher end, that's 19% of your calories from protein.
assuming you are seeking to maintain, you'll be getting between 50 and 100 g of carbs per day (from veggies, it appears! ), which means 200-400 cals of carbs per day. i average about 80 g per day myself, so 320 calories from carbs. that's 17% from carbohydrate.
Thus, the rest will be fat. So, 19% protein; 17% carb; and 64% fat.
Now, if your amount of calories that you take in per day is less -- say 1600 (that's where i am now, roughly), then those perccentages are different. 320 of 1600 calories is 20%. The protein is higher too, you know? it's about 20-25%. And then the fat will be 55-60%.
But those are the rough numbers. and you should be fine.
After you have this part figured out (your maths!), then your next step is to look at what works for you or not. you may or may not have a reaction from almond butter, dairy, and whatever fruits or veggies might cause you problems. try a certain number of days (say 30), and then bring it back in for a number of days and see if you get a reaction. if yes, then avoid it, and if no, then don't worry about it.
but don't really try the elimination stuff until you feel comfortable with your macro-nutrient percentages, and in rhythm with the diet and lifestyle.