Did you go from eating a lot of fatty, processed foods to eating a high fiber diet? It could be that you're body is still clearing all the junk out of your digestive tract. You should try daily enemas to help clean yourself out.
I'm guessing your body isn't used to it. Keep going. :)
If you don't have a personal trainer, you might simply try asking another member. (I don't pay for the personal trainer NOT when the joint is crowded with others eager to offer advise.) What you need to know is PROTEIN needs to be replaced. A protein drink like 'BOOST' needs to be in your stomach after a work out. As if you don't, your body will feed on your muscle if it cannot find fuel in your stomach.
Not used to the new lifestlye?
Lol same thing here