Yes I started my period on the 28th and for about a couple of days now I have had large blood clots as big as golf balls. Is this normal or what should I do

If the clots are as big as golf balls you must see a Physician - soon.

So what could it be, it makes me feel light headed sometimes and I have to change my pad like every 15 to 30 min

You need to see your doctor ASAP. Blood clots this large can signify a miscarriage. Changing your pad once an hour is a serious concern. If you are changing every 15 - 30 minutes, this is usually considered an emergency.