You may be deficient in stomach acid. My understanding is that this isn't uncommon among those who forego meat for some time. Try taking Betaine HCl and/or ACV. Somebody else may know better which is best or how much. I take 3 HCl capsules before each meal and still haven't gotten any discomfort, which is supposed to mean I'm still deficient, which I can totally believe. It's only supposed to take 3-6 months to get a naturally plentiful supply again.
Supposedly another test is the beet test: if eating lots of beets makes your urine pink or red, that supposedly means you need more stomach acid. Heartburn sufferers are also most usually *deficient* in HCl (not the other way around) and usually do better taking ACV (apple cider vinegar, raw & unfiltered, 1T in a big glass of water per day) instead of baking soda - if the ACV helps, it's a confirmation that the problem is not having enough stomach acid for proper digestion and antacids will only exacerbate the problem over the long haul.
Don't know if any of that will help; just wanted to pass along the HCl info since the folks I've heard of having troubles transitioning to more meat have often found that to be the problem and solution.