Image is lacking bright spots so my guess is underexposed as well. Makes the image look a bit grey.
For black and white I always set a white point and a black point (I use Photoshop). The darkest part will then be black ant the brightest, which before was grey, will be white. If it's still to dark one can play around with the settings of the white point but the result will be blown highs.
Hope you don't mind.
White point is set in the glasses to the far right. Black point is in the hair by the ear. The sharpening I added isn't the best but I just wanted to se what it looked like.