Utterly shattered; but I can't be overtraining?

Are you used to doing 4 hard days back to back?

I wouldn't say you can rule it out as 4 or 5 hard sessions a week is quite a lot and if you are not unwell, it seems the only plausible explanation. Your lack of enthusiasm could come from the lack of variety as turbos are not the most exciting place and it could do you good to get outside and do a 'proper' ride. You may find that the wind in your face helps wake you up a bit and that the actual physical sensation of speed could get you re motivated to the bike. It will also allow you to ride more varying terrain so your muscles will get a slightly different workout than a turbo. But assuming you are sleeping and eating enough and are not unwell, then overtraining seems to be the most obvious explanation especially considering 4 hard turbo sessions in a row.

overtraining is a long term thing, I wouldn't worry about that yet. If in a normal week you might train 4 times, then do 4 in a row it doesn't seem unreasonable to need ~3 days to recover.

Can you not do a few races/TTs to break it up a bit?

I am always within 4 - 6 days of my next race at this time of the year, so really do have to think about quality time on the bike. I cannot stick in the constant dripfeed of training sessions that you can seem to do from November to February

Eating more is the first thing I'd suggest you try. Found it was my problem when I was in a simliar situation about a month ago.

4 days back to back of really hard training WILL wipe you out without a doubt, now it might not hit straight away, but it will take it's toll. The damage intensive training does has a culmalative effect, and might take a while to manifest itself.

Training is all about getting the balance of volume and intensity right, and knowing when to ease back slightly. Train hard all of the time, and you will suffer as you just get more fatigued, and depending on other stresses in life you might not be recovering enough between sessions.

Some of the symptoms you state are classic signs of overtraining, and don't think even on a small amount of hours you can't get overtrained, you can do quite easily if you do very high intensity and have a pretty stressful life. The body doesn't know where stresses are coming from, but it does exactly the same for training stresses as it does for other life stresses, too much of either or both together will cause similar issues. Try and tailor your training not to have 4 hard days back to back on a regular basis, in the long run it will likely do more harm than good.

With regards to food, just don't go eating more, you might well be consuming enough food as it is, look at the food you are eating and make sure you eat enough of the foods that fill you up, protein and fat. These help with recovery as well, as does carbohydrates, but just don't go eating a shedload more carbs, as it might have the opposite effect to what you expect.

Also get enough sleep, if you generally feel all over tired, try and get a couple of 9-10 hour sleeps in, this will have a great benefit of getting rid of overall tiredness I find.

Repeated hard training sessions can drain you, i've had the same, despite not doing massive volume in terms of hours, by the end of the working week, I have had times where I was absolutely exhausted to the point of feeling ill. I've general learnt that unless i'm training specifically for a multi-day event, I never do more than 2 hard sessions consecutively. Recovery time is critical.

Agree with others making sure you are getting enough food and the right quality is important. Another good sign of overtraining is not sleeping well. In heavy training I use a diary and make a note of my sleep quality.

Finally, you do mention motiviation. One of the best things I did was find a nice sunny day on a weekend, no HR monitor, no GPS no gizmo's, I just got on my bike and went for a ride for a few hours at effectively a touring pace, with a stop at a couple cafes / pubs. Sometimes I find too much structured training can take the fun out of it, but thats just me.

I've ramped up my training recently from 0-250miles (and still going) per month, i'm using a app that very easily monitors food intake and shows a protein/fat/carb split. It's simple to use, just scan bar code or search for the food item within the app (think its called my fitness tracker/plaanner).

The one thing i would say is i'm quite astonished at the volume of food i can eat and still loose wait (1-2kilos per week), inclusive of a few beers once or twice a week.

Even if you don't want to use an app like this full time, try it for a day or two at least that way you can easily see if your under eating or not.