I have chronic anemia. Been dealing with it for some years.
Take your iron with vitamin C on an empty stomach by itself (with nothing else). "Ironsorb" by Jarrow is a good, non-constipating, economical brand of non-heme (not from animal source) iron that doesn't upset your stomach. Sometimes taking iron on an empty stomach can lead to stomach upset, so be careful what brand you choose.
"Empty stomach" means one hour before or two hours after a meal. I generally take mine first thing in the morning. But DO NOT drink coffee or use milk products or eat anything with a lot of fiber for at least an hour after you take it. All of those things will severely impede absorption. As will taking other minerals with iron or too close to your iron dose.
I also take methyl B12. I get a script for injectable (I inject myself) from my hematologist. It's part of my methylation protocol as well as treatment for anemia. I've had a lot of ups and downs with methylation, but it's been one of the best things I've ever done.
You do need B12 for iron absorption. I take my iron, vitamin C, and B12 shot all at the same time every day. If I do a double dose of iron in one day I'll do it with vitamin C but don't need more than one B12 shot in one day.
I also take adenosylcobalamin because of methylation but also because of anemia. I think both are needed to absorb iron properly.
Also take extra antioxidants, because iron is a source of free radicals. It's not to be feared unless you go into iron overload, but just to be on the safe side, take plenty of vitamin C when you take the iron, and then other antioxidants later.
The racing heartbeat: as melamine noted and others noted, the hydroxycobalamin may have kickstarted the methylation process for you. I second the recommendation about adding some daily potassium supplement to your diet. I like to put powder in juice .
Word of caution: if you keep on with the B12's, and add adenosylB12, you may run into problems of needing folate and other supplements. It's a great thing when your metabolism ramps up but can make you feel worse before you figure out what you need to feel better. Just be aware of this if you continue taking B12, especially if you add the add the adenosyl. Not a warning against doing it, just something to be aware of as you learn more and experiment with other things.
Good luck!
P.S. Not busting your chops
, but pernicious anemia is a diagnosable disease, not just regular old chronic anemia. PA is not just from eating a low iron diet, or from other identifiable causes (blood loss, etc.). Pernicious anemia stems from autoimmune causes which damage the ability of your GI tract to absorb B12. Unless you've been formally diagnosed you can't know if you have it. Probably better to say you have chronic anemia unless/until you receive a diagnosis of PA.
P.P.S. I posted this without realizing it was a 2-page thread. So some of what I said here may have been said by others. Apologies for any redundancies. I don't really have time to go back and read and edit appropriately.