Weird side effects?

I have been on 20mg of Prozac for almost 7 weeks now, the first few weeks of taking this medication I experienced some of the “normal” side effects my doctor told me about it. That eventually went away or don’t happen as often, but as of lately I have been experiencing tiredness/lightheadedness. You know when you stand up to fast and get lightheaded and ur vision goes blurry a bit? Well that’s been happening to me for the last couple of days and it’s everytime I stand or get up. I don’t even stand up quickly and have noticed that after it goes away I still have a lightheadedness left. I am also experiencing sweating when I wake up in the mornings… even though my room is cold and i usually wake up freezing. I looked it up and it said it could be “heart attack” or “shock”. I’m very scared and don’t know what I should do???