Struggling with fussy baby

I'm really drained right now from the CONSTANT moaning, crying and whinging. It's all day, every day and only relents when she's eating or sleeping. I'm finding myself putting food in front of her all day long because it's the only time she stops shouting at me for 5 mins. There's no apparent reason for the constant complaining. I really am losing my mind with it. I'm getting very frustrated with her and I know she isn't doing it to annoy me but it's really really testing my patience. She's been ill and has had a molar come through in the last 2 weeks so I can understand that a lot of it was probably that but I don't think she's in pain anymore because as soon as I pick her up she will stop. But I can't just walk around holding her all day, she's so heavy and my back is breaking. Even in the carrier it's too much. I have been ill for 3 weeks myself and honestly I'm so tired, drained and I just want to lay down by myself and not have to worry about taking care of this angry old woman who seems to be inhabiting my baby's body. What is going on here?? It's been weeks of this now. Plus she's stopped napping for longer than 30 minutes so I'm getting literally no rest all day. I just want to cry all day long.