Tax credits and self employed help

ellionic

Hi my boyfriend has just became self employed after being made redundant in November. He works 30 hours a week for a local taxis firm and was earning £95 a week which is not much to start with but he says he would rather do this than be on JSA. This month his income has dropped to £80 a week i have informed tax credits and got my new award this morning but i am confused as to how they work it out.
I told them that we were £15 a week down on his wages so thought we might of got a couple of pound more tax credits a week but we are getting £5.00 a week less than before his income dropped. does this sound right? I know £5 is not a lot but we are struggling to start with.