Just keep going slowly. Chlorella is very effective in killing candida and other pathogens in your system. The unfortunate thing is when these fungi and bacteria die of, they often release toxins into your bloodstream, giving you some of the symptoms you're reporting.
Also, drink lots of water to help flush out this junk.
Keep working up slowly. If this continues to be a problem, perhaps you do have an allergic reaction to it which some people have. But more often than not, it's just part of the process of your body adjusting to it and cleaning out.
to keep you motivated, here's a great article on why chlorella can make such a difference. I was surprised reading this: