B Vitamins are also really good for picking you up, could be a variety of things really...
Are you drinking enough water? sometimes something as simple as dehydation can really stuff you up - not to mention make you forgetful at times.
I would go and see your GP and have a electrolyte panel done (simple blood test) plus or minus anything else that they may want to check...

Are you sleeping? Bubs keepig you awake? you could just be run down and tired, lask of sleep is awful - there is a reason why it is a form of torture!!!

I also agree with Catherinemoses, getting some exercise (even though it probably is the last thing that you want to do) will help boost your energy and send all the sluggish blood around the body quicker and flush out toxins...

Hope you are OK