Do you have any flashing lights with this? Do you have any headaches? Is your vision worse?
You may be experiencing a floater. This occurs as we age when the gel in the back of the eye breaks into little pieces and float around. Eventually, it sinks down out of our line of vision. However, at times such as when we are laying down, it can float back up until we get up for a while (then it will sink down again). These are annoying but harmless.
Another possibility is an ocular migraine. These can present with blindspots in your vision and/or flashing lights. They usually last 15-20 minutes. They may or may not be followed by a headache.
By the way, you don't have to accept the generic (unless you want to due to the cost).
Hope this helps.