There are 2 main possibilities:
1) Vitreous detachment. This is very common, and results in floaters. I have it in both eyes. I have had no treatment beyond a careful examination by the best optometrist in town to rule out a -
2) Retinal detachment. This is not rare, is accompanied by floaters and can result in considerable loss of vision if not treated very early (typically with a laser to stick your retina down before it detaches any further.) There are more extreme treatments for more severe cases that I won't go into.
A retinal detachment is a very big deal and my advice is to have it ruled out the same way I did - by having an immediate exam by an optometrist or ophthalmologist. Having had a complete eye exam a month ago does not rule this out.