Hi, I hope someone can help me regarding my situation.

I'd my first job as a Chemist from July 2015 - March 2017. And then, I got my second job as a Laboratory Technologist but I work for awhile from May 2017 -June 2017. My second job is more related to my field of study which is Biomedical Science. However, I left because I was being treated very unfairly by other colleagues. My supervisor also not a supportive when I joined in. And the work is quite a very fast paced environment and I realised I slower than other colleagues.
So, I quit my second job because I feel really stress and feel the job is not a right fit for me. I left without having another job.

Should write my second job in my resume? Do I need to tell the interviewer about my second job?
What reason should I give to the interviewer about the job gap? What should I say when the interviewer ask what are you doing during the unemploment period? I still unemploy until now from June 2017.

Please help me.
Thanks.