I guess there's no way of knowing till you stop, is there.
There are a number of other things I could put it down to - sleep (though it's only a couple of wake ups a night at the mo - early starts though), being a new mum, anxiety about returning to work soon, low mood at times, struggling to find time to exercise properly (which I used to rely on to keep my mood even), eating too much or too little - not sure...
I am just so very tired. Little one is 9 months old and eats well, and doesn't feed that often (maybe 4-5 times a day now, and one night feed). I get 7 hours sleep a night if I go to bed at 8pm or 9pm (which I do, even if it's killing what social life I had left) and I know she is a good sleeper for her age and I feel guilty that I still can't shake the fatigue.