I recently (Dec 2018) tried to enter the UK after traveling there for a week prior to December with no such trouble. This time however, I was trying to stay for 6 months to be with my boyfriend (UK citizen)... (I know bad move) Naturally and quite stupidly I quit my part time job as I thought I should to go on such the journey. I did not have any money for this trip as I would be relying on my boyfriend to "support" me during my stay there. I did not see any issue in doing this just as long as he could prove his source of income.
With this, I opted for the 6 month instead of say 2 weeks or 2 months (like I should have), i.e. I wanted to spend the most time with him that was possible, then go home. Anyways I was denied entry and sent home due to 'insufficient funds'; e.g. I quit my job in order to come on this trip, so to them I looked as if I cut all ties with my country, when in reality I was just trying to spend some much needed time with my boyfriend.
Long story short, if I try to reenter for two weeks, will I be denied again, being as from the nature of my second visit I was deemed a 'non genuine visitor"? I was told I was better-off applying for a visa. I was just genuinely confused about the rules on going for 6 months as you do not need a visa to visit up to 6 months if you are from the USA. I just want to make sure once I decide to travel again I won't have any hiccups.