I agree, I think you are worrying too much. I've been 4 times... never brought any proof of work or ties to the US. Each time just had a itinerary with a round trip flight. I've been through when I was let in with only two questions asked, received a smile and a stamp. I've also been through where I was questioned for 10 minutes and the officer threatened that if I didn't leave the country on my return flight then there would be problems. I was re-entering the UK after being in Europe for 3 days. I thought for sure he was going to take me away for further questioning and I wanted to cry. Luckily he didn't. That was before I found this lovely website. I realized the IO's do see a lot of women everyday who are going to visit boyfriends in the UK, so of course they have to make sure people aren't coming in stay illegally. They may ask some personal questions and some IO's are going to be more stern than others. They may ask you how you afford to visit your boyfriend, how you keep in contact, if you live by yourself, if your parents give you money, where your boyfriend works, if you plan to get married soon, ect. Just be honest with them and don't act nervous and you should be fine.