What if I have lost my sense of purpose?
That wouldn't be good. What was your sense of purpose?
Secretly I used to help homeless people.
I can understand you losing your sense of purpose. You should really try not to give up hope on certain things you do in your life, you should try to reflect on what gave you purpose and try to find the mindset to continue to do those things to regain purpose in life. Continuing to dwell on not having a purpose will not change anything without action.
It is hard to get back to it. I'm in a very ignorant place in my life where I want to keep doing drugs and having sex without seeing a future for myself.
It is hard to go back to what gave you purpose but it is possible.  You shouldn't give up trying to get back to it. It would be better than to waste your time on what you are doing now.