Hi! I have very similar problems to you in terms of digestion and I have candida! Since you also have the rashes and things it sounds like your problem is very candida like.. I'm surprised that your stomach problems have improved from garlic and vitamin c as well as having die off.. maybe it also has something to do with you changing your diet? I haven't found much to improve my digestion yet.. But if you do have problems with indigestion and food sitting in your stomach and feeling full and whatever still you probably have low stomach acid and maybe a lack of digestive enzymes and you really need to get your digestion working again or you're probably not going to be absorbing many vitamins and minerals from your food.. if you've ever been given stuff like antacids to help you're definitely doing the opposite of what you should be.. you can find a lot about low stomach acid on the net and there are lots of things that can help.. you can send me a PM about it, but I'm no expert lol! I got a lot of help from the people here actually
Also! You probably need to eat more vegetables.. a lot more vegetables! Things like meat and refined grains or sugars are all very acidic foods.. so if you have eaten a diet with predominantly these foods you've probably messed up the pH balance in your body and you need to make it more alkaline (btw if you're confused.. alkaline foods im pretty sure don't lower the acidity in your stomach, but they lower the acidity in your blood) sometimes you have to do the exact opposite of what you've been doing to get better.. raw vegetables are probably better to raise pH, but if you have digestion problems they might be difficult for you and it's better to have them cooked.. like steamed and whatever.. juicing is also a really good way for you to absorb all the minerals and vitamins from veg because you don't have to digest them.. also you should take probiotics, it's best to make fermented food like sauerkraut, kefir, kimchi or yogurt.. it's really better to make your own because store bought ones have a ton of crap in them.. sauerkraut is really easy to make
I'm also only 21.. our modern day diet and lifestyle really screws us over! As well as our reliance on drugs to cover up our problems, but not actually fix them.. doctors don't know much when it comes to nutrition.. they don't have much training in it so you're probably better off not listening to most of them. I think so many people our age are gonna end up with these kinds of problems eventually because we all just continue to eat fast food, drink tons of alcohol, processed food.. it's important to realise that even if you do get rid of your problems it is never a good idea to go back to eating that way even if it is really difficult
You should also try to find ways to manage your stress if you get anxiety and shit.. it's lame, but you should never get too carried away with things.. getting good sleep and keeping a calm mind are just as important as everything else in this.. having tons and tons of die off isn't really the best thing because it can cause a lot of stress on your body.. so don't try to put too much pressure on yourself!
Anyway sorry for writing such a long post i always get carried away >< and in case anyone is wondering I'm not a fisherman!! I just don't know how to change that picture :(