I am afraid of you (φοβουμα υμας). He shudders to think of it.

Lest by any means I have bestowed labour upon you in vain (μη πως εικη κεκοπιακα εις υμας). Usual construction after a verb of fearing about what has actually happened (μη πως and the perfect active indicative of κοπιαω, to toil wearily). A fear about the future would be expressed by the subjunctive. Paul fears that the worst has happened.