Englishman in Miami

Hi,
I had a very similar situation. My boyfriend at the time was a US & UK citizen but I was only a UK citizen. For a few years we could not get married as waiting for his divorce to finalise. So like you came back and forth for 3 times.... I had a 'B' visa so I could stay for up to 6 months at a time, but only stayed back in the UK for a month before returning.
On my 4th visit back flying through Atlanta, the pulled me over, interegated me for a couple of hours, treated me like a criminal then told me " I was living there" ! (Which is not allowed) and that if I didn't agree to being deported I would be put in a cell over night and put before a judge in the morning and if found guilty, would not be allowed back in the US for 10 years, I said they left me no option, so was put on the returning flight back to the UK.  No one told us you had to stay OUT of the US for at least 6 months.  We went to the US embassy and they advised us to apply for a fiancé visa. Which we did and it took about a year!!  Eventually I got one flew back the US and we were married within the 90 days. The lived there for the next 10 years, within that time I received MY US citizenship.
So in answer to your question.....YES.....get a fiancé visa ASAP before they deport you.
Barbara