Where did I go wrong?

I'm 30 years old and feel like a complete failure.

I started in the work force very young (16) and was so driven to work and earn money. I had a job with a lot of responsibility and I felt amazing knowing I was capable of doing the job well.

Then came along my husband and children, which I had young as well. I had a big battle with post natal depression as well as dealing with emotional abuse from my husband. 4 years ago I separated from my husband, and at first it was like a weight had been lifted off my shoulders and I felt on top of the world.

Fast forward to now and I'm struggling with everything! I run a little business from home but it feels like a constant battle to keep it going and it barely brings any money in. Just enough to keep a bit of food on the table. I've been applying for jobs in the area of work I used to work in just so I can pay the bills which I'm behind in, but I've so far been rejected for every job.. Not even an interview.

I've been seeing a man for about 2 years now. It's been a tough relationship, but I think we've nutted out the issues. He's a wonderful man, helps where he can, but there are times when I think I'm not good enough for him. We have been talking about moving in together for the past year but so far it hasn't happened (because of reasons on his end). I feel like he might be stalling and I'm starting to wonder if it'll ever happen. I miss the feeling of falling asleep next to someone. I feel so alone at times that I can't help but sit here and cry.

My kids have turned from the beautiful well mannered appreciative angels they once were to a constant struggle. My 2 youngest (9 and 7) are such a handful. My 9 year old in particular has become selfish and demanding. We can't go anywhere without tantrums because I won't buy her anything. They do chores and earn pocket money, but it's still not enough. She has resorted to stealing money from me and her brother. She was punished both times but I'm not sure if she's learning right from wrong, and I can't help but feel like she's going to go off the rails when she hits the teen years.

I feel like life is a constant struggle, emotionally and financially. I have no assets, just a heap of debt and it plays on my mind when I see people younger than me who seem to have their shit together and wonder where I went so wrong. I thought by 30 I would have clear direction, a career, have my head screwed on, and be settling into life.

Does life ever get easier? I'm tired of feeling so lost and like I'm failing everyone around me :-(