What are the possible causes of dizzyness on P&B

I am on day five and am taking two P&B shakes a day. My diet is about 80% fruits and vegetables and recently Miso soup. I haven't passed anything abnormal yet but have got a bit constipated so am increasing my water intake.

I was fine for the first two days but for the last three I have woken up in the morning very dizzy and disoriented. Today I mowed the lawn and had to lie down due to the same symptoms. Later today I cleaned up the yard and again got dizzy with a headache.

Possibilities?
1. Change in diet has affected my blood pressure or Sugar levels? I wasn't that big a meat eater before but am missing dairy and breads.

2. Toxins released from the cleanse are overloading my system and this is made worse by the constipation? Is it too early after only 5 days for this to be probable.

3. Bentonite has absorbed necessary nutrients and I need a supplement? Bentonite is interfering with absorption of nutrients in food I eat?

4. Any suggestions?