Boston fern is a weed species. In my neck of the woods, coastal central California, it grows outside and can be invasive. I have it running amuck in my back yard!

I think that the first thing to consider is your water.
Are you using softened water? If so then that is the problem. Use rain, distilled, or deionized or reverse osmosis water for your plant. If it is in regular potting soil then water once a week and that should be enough. This fern can handle some degree of dryness.
You may want to tap the plant out of its pot and look at the roots. One problem that I have noticed are mealybug in the roots of this type of fern. If you see alot of white fluffy stuff along the roots then I would dump the plant and buy a new one. In fact I would be glad to send you some for postage!