Do you think I should go to the doctor to find out if something is wrong with me?

For awhile now I've been feeling weak, tired, sick, and when I get up from my couch[or im just walking] all of a sudden my knees get real weak and my vision goes blank and i wobble. I frequently get headaches and my vision is getting blurry! I used to have perfect eyesight.. My diet hasn't changed at all. It's always been pretty much the same. I eat three times a day, and I excercise. I think I should see the doctor.