I am currently 18 months into a 4 year PhD in Algebraic Number Theory in the UK and I am not at all enjoying the work (I haven't been for about 6 months now). This is not because I am "stuck" - I am not really at a point where I have been able to engage enough with the work to even become stuck. The problem is more motivational: it turns out that I just don't have any interest in my particular area and so I spend most of my time either worrying about working or worrying whilst working - very inefficient! The area in which I work is also quite small in the sense that very few (in fact, only one that is comprehensive - as far as I am aware) textbooks have been written on the basics and even my supervisor admits that these few books are exceedingly dry.
With all this in mind, I decided recently that I will leave the PhD and do something else (I actually have no idea what yet). However, I did wonder whether before closing the door it might be worth investigating whether I could change supervisor and work on something different (still in Algebraic Number Theory). I guess my question is whether others on this site (PhD students or PhD supervisors) have had a similar experience or have any advice regarding this situation?
Note. I have no doubt that this post will almost instantly be marked as "off-topic" - however I really think that it is difficult to obtain the opinions of professional mathematicians on other forums whereas (quite often) they respond to questions of this type on this site.
Many thanks!