In the last 3 days I've had 2 'attacks' which involve dizziness, severe nausea, extreme weakness, slurred speech, vision&hearing effected. What could it be?

Get seen today! These are worrying symptoms, you need to get checked to be sure nothing serious is going on. Get seen today, if you cannot see your doc today, go to an ER. An in person exam is essential, unless you talk to your doc and a better assessment is made by phone. Do either today. Why wait to get worse!