visual disturbances

I have  had floaters since Dec., which I have had checked twice before by my eye dr.  I  am 38 weeks pregnant. Last week I was at work and had an ocular migraine. I went in right away to  my eye dr which examined me and said my eyes  look good and then told me that it was an ocular migraine and said I may or may not get one again.  Now I have anxiety so  everything just makes it worse and one of my fears is a brain tumor.     I asked him if this was a neurogical thing and he assured me it was not. Iwent home feeling good. Then today I  read someone on medhelp.org (I can't  quite remember where) that ocular migraine stem from more serious things (blocked arteries in the neck/brain, heart cond.,etc.) Is this correct?  And if I had my eyes examined (3 times now since Dec) should Iworry? Does anyone else get these and know what they are caused from?