archergirl, I agree with much of what has already been posted here, but I felt the needs to add my 2c worth.................
I also have Neptune conj MC - but my Neptune is in the 9th - and have had moments of longing for the `singing career I almost had', but baulked at when I truly had the chance (sometime deep in the 60's, I think it was). Neptune conj MC can make one quite dreamy/unrealistic about the details. It's the idea, the feeling, the imagined emotion of the dream which can drag you in, but the reality is frequently something else again.
No-one seems to have picked up that you also have transiting Pluto squaring your natal Chiron - placed in Aries in the 2nd, which can make you a bit hard on yourself, perhaps dissatisfied with a job well done.
Pluto's square to Chiron is likely to get under that skin of `what if?' - to lead you to re-working some ideas which were left unfinished - and the square of tr Uranus to your Sag sun adds that boost of 'oh, what the heck - why not?'
According to Martin Lass, this is a major transit of Chiron, and forces you to dig deep into your wounds in search of new solutions to old issues. In your case, the issue appears to be one related to your worth, and how you have always measured it. If you don't pursue the singing career, or if you pursue it, and you get nowhere, what will be your own assessment of that? You may need to look for a different perspective of yourself through your sense of what it is you believe you have to do/be in order to live your life well.