I used some of my Origin points to buy dlc for either ME2 or ME3, but for some odd reason, it's not letting me do it anymore. Did they disable or discontinue that feature?
According to this question and also this thread on the official forums, you can't use Origin points to purchase anything. They are solely used to show off your skills in participating games. You are probably confusing them for BioWare points, which are used to purchase DLC for older BioWare titles.