Um, Tuesday wasn't the 9th; do you mean Tuesday the 6th? If so -- you said Tuesday you began spotting; when did you begin bleeding, many days ago or just yesterday or the day before? And was this pad-per-half hour rate going for more than a day? If you are filling a maxi pad in less than an hour and lying down and keeping hydrated doesn't calm the bleeding, then go to the ER.
By "last Tuesday" (when you started spotting) do you mean Tuesday two days ago or Tuesday 9 days ago? If you have been bleeding for 9 days and have to change your pad every 30 minutes, go to the ER (and while you're at it, take some iron). If you started spotting two days ago and now it has progressed to bleeding, it's a good idea to see your doctor anyway if things don't calm down by tomorrow morning. Stay off your feet (to calm uterine contractions) and drink water to stay hydrated, and if you begin passing large clots (size of your hand), go to the ER.