you are probably depressed. you might not even know about it, but you are probably not very happy at the moment.
people lose their concentration when they are not happy, or preoccupied with other other things.
if they start thinking bad thoughts and are losing their concentration, its probably because they are not getting what they expect from Allah.
you need to refresh your mind. you need to fill yourself with hope. hope that Allah will save you, protect you and help you.
people will tell you to become more religious, read more quran, pray more, etc...
but really, you need go on a vacation. do something fun. you need a break.
do you suffer from stress? are you a stay-at-home mom? if so you, need to get out a bit more.