I would definitely be worried about this. For me sleep disturbances are one of the earliest warning signs. In your case it sounds to me like it's maybe already getting past early stages.

With regard to Seroquel, lower dosages work better for sleep than higher dosages. For me 50mg XR works best for sleep, although some people take as little as 12.5mg. Sometimes after a while the sedating effect lessens. In that case I sometimes find it helpful to cut out the Seroquel for a day or two so that it works better again after that.