I am lactose intolerant. Can i use non chalav Israel lactose free product when I usually only use chalav Israel?

Thank you for your question. Yes you can. You can rely on the poskim (Igrot moshe, chazon Ish and others) who are lenient about the non chalav milk in our days. You also don't have to do a hatarat nedarim because you probably didn't accept upon yourself to me machmir about chalav yisrael in any case (even though you usually only use chalav yisrael). additionaly you probably did hatarat nedarim before rosh hashona or kol nidrei on yom kipur. All the best!