It is better for you to have an eye exam and make sure what strength you need for prescription reading glasses. If you have difficulty in reading and are over 40s, you can wear reading glasses.If not,you will need - powers because you are nearsighted.reading glasses usually come in + powers and just magnify up close for people over 40 or so and have trouble to see small print up close.
According to your description, you are just nearsighted. So, you needn't wear bifocal glasses. A pair of single vision glasses can meet your needs. And since your prescription is a little bit strong, you'd better choose high index single vision lenses such as 1.60 lenses. Or your may got a pair of thick eyeglasses lenses. Good luck.