Visitor Visa - B2

Hello all. I need your advice pertaining to re application after being denied a US B2 visa. I had applied a few weeks back but unluckily was not granted. I was handed the 214 denial paper. During the interview, the officer asked me what my reason was, so I told him I wanted to visit NY for a few days. It was mentioned during our convo that I have an American boyfriend of almost 2 years and that we will both be paying for the entire trip and stay. The other things mentioned during our talk were the following:
> Occupation: Supervisor in a Casino
> Personal: I have a son
> What countries I have been to: told him all the places I had been to

The officer was grumpy the whole time, sighing every time before or after he said something. Even before the first two applicants before me. The one before me got denied too, but I didn't listen to their convo. It was a frustrating day!

I only wanted to see NY with my BF for at least 12 days. I cant stay there for too long cause I have a job to do back home.

I have no idea which part has made him give me the refusal. Anyways, I'd like to see if anyone here can give your expert advice on when I should re apply and what I should do when I re-apply. On the blue letter it says to show stronger ties to my home and to show changes in my circumstances.

I would truly appreciate your help. Thanks in advance.