Re: Feel so unwell when eating well ...
Yeah. Eating terrible food for a while then cutting it out completely (especially if you had chronically elevated insulin/blood sugar/serotonin levels from the processed sugars you consumed) can make you feel pretty damn bad.
However, I think your body is probably screaming at you "more calories and protein!" - in which case, keep the junk out but add some good, calorically dense food (consider meat if possible) in.
Though I realize, since it seems like you're detoxing, that doesn't seem reasonable. Well, if you want to be detoxing, you mostly should just suck it up. Eat an avocado or three, maybe. Find some good proteins that you can work into your current dietary plan. When I was detoxing, the low calories were killing me, but I managed to find ways to bump them up.
In general, though, this is somewhat expected - it's partially symptoms of withdrawal from addiction to the effects of your own insulin. Bite the bullet and wait a while. If you're getting enough protein + cals in, but still feel this bad, then by all means, make some serious dietary changes that do NOT involve adding junk food back in. Eat nuts, or meat, or whatever - anything rather than add back in the processed crap.