Someone please help

I've received a letter from dwp saying I have to attend an interview as they are reviewing my circumstances and benefits. If I do not go they will stop my benefits. I'm worrying thinking why have they sent me this what have I done. I suffer with anxiety and I'm on sertraline have been for over a year...I had my second baby two weeks ago and I am currently trying to sort my benefits out by adding him to everything I.e child benefit etc. I am a single parent to 2 beautiful boys I'm just scared they are going to stop my money. I will be going back to work as soon as possible as I want the best future for my boys. Has anyone else received a letter like this? What was your experience. What could it be?