I wouldn't worry about Mother's Day, but I stand for "effort is the best indicator of interest". Christmas,Birthdays, etc. are quite important to me, so I understand your concern. I have been in relationships which my boyfriends 'forgot' to buy me a gift and not long after we split up.. of course it wasn't a a reason why it happened, just saying that if someone stopped making the effort (to keep you happy) its usually a red flag, IMO.