When Is My Credit Score Going To Improve?

I have been very good with credit the last few years. I have not used any credit cards and have been paying off my balances. So much so that the balances are now under my credit limits. But my credit score is still poor and not improving. I used to check it every once in a while with one of the free credit score  sites and saw no improvement. I then decided to get serious and got a  FreeScore membership and now check my credit score and report every month. But I still see no improvement. What gives?

I think I read somewhere that it is harder to have a good credit score now. Not sure of the details of the why or how, but that the numbers have been tweaked. What used to be a good score is now just a fair score. So maybe that is why mine is still in the toilet? I did have one collections item added to my report--when I switched from comcast to ATT, there was a balance with comcast I forgot to pay off.  That must be the problem. Maybe if I go ahead and pay that off, it would go up.

I know Dave Ramsey says not to worry about credit scores or reports. That you shouldn't rely on credit anyway, so a bad score doesn't really matter. That is good in theory, but not so much in reality. I want to buy a house in a couple years, so I am concerned about it. Maybe it will be better by then.