Is it safe to have anal sex with non-painful internal hemorrhoids? It was caused by not using lube before, but I always use lube now and am w/o pain.

Not Recommended. If you have internal hemorrhoids, i would recommend against anal intercourse as this can exacerbate the issue whether lubricated or not. If they are in fact internal hemorrhoids, you can consult a surgeon for banding to improve or resolve the issue. Meanwhile, to reduce flares, also avoid straining and keep stools soft.
Maybe. Internal hemorrhoids usually don't hurt but can bleed painlessly. Any activity involving penetration of the anus has a potential risk of infection, sphincter damage, tears, bleeding whether or not lube is used. Generally, the anus is an exit not an entrance.