This is a one handle faucet and it moves by a "ball" in the center. There used to be a screw in it I think but I don't see one now. This sort of happened all at once too. Is there an adjustment in there that may be causing the low pressure?

Is your faucet a Delta? N How old is it? I can tell you what's happening, ( you have some debris in rhe val ve or supply that's stopping the flow) But I'll need more details before I can give you a solution. Back to upu, Tom