OP, I don't know anyone who is mortgage free by the age of 40. If your DD has a roof over her head and everything that she needs, then you are doing OK.
I became a single parent when DD was 4. I was 40 when XH left, with a mortgage of £110K. I had left a secure job of 20 years the year before to work self employed around DD's preschool hours. I had to re-mortgage and was then mortgaged until I was 67.
I had to pay the mortgage and everything on my own. Initially I got WTC and as I built up my part time business into a full time income, the WTC decreased and I became totally self sufficient within a few years.
I overpay the mortgage now, but have only been able to do that for the past few years and DD is 16 now. I am on target to be mortgage free by 62 now, and hoping to even get that down to 57.
When DD was young, the priority was mortgage, bills, food, DD's clubs.
Stop stressing and worrying about it. While DD is young, you need to concentrate on bringing her up. Pay the mortgage. Pay the bills. Give DD as good a life as you can afford.
Save money if you can towards the future, or towards paying a lump sum off the mortgage once a year, but don't go without food or anything else to do that.