Another thing that can make you tired is circulatory problems. Why not go to the doc and explain your symptoms and see what he recommends. It's the only way to know.
I am pregnant and I have found if I do not eat a small snack between breakfast and lunch that I will be dizzy and I cant hardly see, its as if my eyes are crossed but they are just blurry. Try taking a HPT.
I cant get pregnant and my boyfriend cant get me pregnant.
I dont know what it could be though.
And have you taken a home pregnancy test? Both temporary dizziness and sleepiness do count as possible symptoms.