I feel I have been very sad lately.
What's been making you sad lately?
I have been busy with everything.
Having stress in your life is a normal thing but persistently feeling sad could be a sign of a more serious mental health issue. If you have trouble resolving your sadness, it would be a good idea to speak with a mental health professional to help work through the issues that you are experiencing.
I don't care. Life is too long for me to care for what others think. I don't need to see a doctor either.
You sound in need of a pick me up. You might be getting burnt out from over working. Take a break from all your worries and set some time for only yourself for a week to enjoy.