What can cause numbness/tingling in my hands and fingers? It effects my head too, makes me feel a little cloudy. ;t gets better when I sit but standing it aggrevates, makes me feel weak...?

Many possibilities. There are quite a few possibilities for the symptoms you describe - from low blood pressure on standing (with many causes), to anxiety with hyperventilation, to a low calcium level, and peripheral neuropathy. Best to get checked out if this hasn't resolved on its own.
Many issues: BP? Med. There could be many causes but your blood pressure and medications come immediately to mind. You need a full examination by your primary care physician as well as a review of your history and medications along with possible diagnostic testing.