As with many others who have already responded I have been through much what you are going through now. I also was studying business while working full time in a chartered accountancy firm. Much like you it wasn't exactly what I wanted to do. Though I did see it as a stepping-stone. Something solid to get under me which I could always fall back on. Then I caught glandular fever, which ended up turning into chronic fatigue. Eventually I lost my job and essentially failed uni.
After spending some time focused 100% on regaining my health I returned to university. Only this time I had a lot more life experience behind me. Much of what I went through is irrelevant here but one specific thing is.
Right before I started back into uni I came across an exercise for motivation, which I worked through. The result? I completed 17 subjects in just 15 months getting results that anyone would be more then happy with.
You can check out the exercise I used and what I learnt regarding what motivation is and how it works in my article
How to Stop Procrastinating, Get Motivated & Achieve.
If you want to get through your university studies then do the exercise described in the article. There is nothing special about me. I just learned from others that we can program ourselves to achieve whatever we want. It worked for me and it will work for you.
I wish you the very best for the future.
Stephen