Yes, mucus in the eye can cloud your vision for a brief time, if it lands itself in your field of vision. I don't do the eyewash thing because my eyes are severely dry and very sensitive. But it could help. You could also just try flushing the eye with some preservative free artificial tears when you get the sensation that there is mucus (or anything else) in there.
High Inta-Ocular Pressure (the blood pressure inside of your eye), if left untreated can lead to glaucoma and vision loss. But there are treatments for it. You can use drops called anti-glaucoma drops to bring the pressure down. If it is extremely high they might perform a laser procedure to bring it down if drops don't work. But lets not jump the gun here. You haven't even been examined yet.
If you had something in your eye (you said that in the past few months some things have gotten into your eyes) believe me, YOU WOULD KNOW IT! You would be in pain, and you'd probably have a corneal abrasion or worse by now. Unless your tear production is greatly diminished, most of the time such debris (such as tiny things like pieces of dirt, etc...) would be washed out by your own tears and not stay in there for very long.
Mucus won't injure your eye, but it can stay in there for a long time until it is washed out, and it can cause you pain and discomfort and irritate the eye.
I still recommend getting a full eye exam to find out exactly what is going on. The eye dr can give you an allergy drop to help with the mucus, and check your intra-ocular pressure and hopefully put your mind at ease.