I bought my house in Oct 2018 and didn't do anything with points. Can I still use points?

Did you actually pay points at the time? If you paid points and you meet the tests to deduct them, you have the option of deducting them all in the year you closed, or, spread out over the life of the loan. That means that you would deduct 1/30 of the amount of points per year over a 30 year loan.  At this point, you could go back and file an amended return for 2018 to report all the points if you qualify, or you could begin deducting the points starting on your 2020 return and the points deduction for 2018 (2 months worth) and 2019 (12 months worth) would be lost.

If you deduct the points spread out over the life of the mortgage, you are allowed to deduct the remaining leftover points if you refinance with a different lender, or when you pay off the loan by selling the home. If you refinance with the same lender, you must take the old points plus any new points and spread them out over the life of the new loan. You don’t have the option to deduct them in a lump sum when you refinance with the same lender.