Well James, my first thought was "perimenopausal hot flushes"...but since you're "James" and not "Jamie" I'd guess we can rule that one out...!
The reassuring news I'd say - and I too am not a doctor, not medically trained in any way except by circumstance - is that symptoms such as you describe can be caused by a host of things, many of them minor. For example, some medication can cause vasodilation (which is where the surface blood vessels open up to circulate more blood, causing the feeling of extra warmth). My thought here is, are you on nicotine patches to help you stop smoking ?
Also, many an otherwise undetectable virus - for example, the family of viruses that cause colds - may trigger an immune response which involves an increase in temperature. (You might not get any sniffles, because they come only when the virus is replicating furiously. Some viruses will lurk quite contentedly where they land for years, asymptomatically.) Depending on how you measured your temperature - some thermometers are not so accurate, or are harder to use - my guess for what it's worth is, you might feel a difference in temperature, even though one might not be measurable.
Tiredness again is often a symptom of immune system activity. Also, again, it can be a symptom of almost every ailment known to (wo)man. Not too surprising when you think about it. So if you have gained weight, lost weight, changed your eating habits, been on holiday, been on medication, come off medication, moved house, changed job, or have a family history of who- knows-how-many disorders - then this may be the cause of such symptoms as you describe.
The bottom line is: if you are concerned about this, the best way to find out is to go to a doctor who will be able to examine you, take a full medical history to rule out which causes are unlikely, and quite possibly give you a reassuring answer.
Of course you are welcome here, but this forum is not really the best place to start off looking for answers, it relies on having some answers already - it works best for those patients who have already ruled out many of the common causes, and know that what they have is not so common.
Hope this helps. Do please let us know how you are getting on ! (Even a negative answer is part of the overall picture.)