what could be causing this?
931557
It's possible you could be pregnant, if your sexually active. You do know that you can still have your period when your pregnant right? If your not pregnant, your internal hormones could be changing. As you get older this tends to happen until ...  the dreaded menopause. There's the possibility of it being the symptom of an STD or bacterial infection. Either way it would be good to see the doctor, especially if your having unprotected sex.
404922
It may be over-heating
876288
What kinda problem can that be?
402404
could just be stress\nbut best get checked by a dr
968967
Are you taking drugs or drinking heavily.  That could cause it.\n\nCoach
14788
There are many possible causes, from stress to allergies to stomach acid to nutritional deficiencies.  Read the site linked below for more information.
808866
possibly could be caused by allergies.
139456
Yikes, that must be kind of scary! Ask your doctor, since no one else answered, and I have no idea what could be causing this.
535622
No but I would talk to your doctor and see what is causing that.
993744
IT COULD BE STRESS OR ANXIETY
115316
It sounds like it could be. Please see a doctor as soon as possible, like TODAY!
292545
Lots of things can. Flu can cause it. Taking some medicines such as some cholesterol drugs can do it. If this is a problem, ask a doctor.
829640
might be see a doctor
59837
could be many things, see a doctor
697553
You should see a doctor ASAP, it could be an infection or a tumor.
258845
From what I have found, there are no medications that will cause it. The exact cause is not known, but usually, it is secondary to another problem, such as infection.
35509
There are a lot of things that could cause this.  You really should get it checked out by your eye doctor just to make sure it isn't a sign of anything more serious.