I always have this worry too. DF is always telling me to calm down. Glad he's the one making the trip this time (next week!) because he never seems to worry about coming in the US.
We average 3-5 months apart at a time, with visits so far between 3 weeks and 3 months duration. His next time is for only 2 weeks, and he'll be here again in the fall for our wedding before we move to the UK. I've only been to the UK 3 times, for a total of 6 months in all, but each time I worry like crazy. Except the first time, because I had no idea I could be told to go home...and I'm pretty lucky I didn't, I'm sure, because it was a brand new passport, my first international travel, I was alone, and I was only 18 years old. I even told them I was there to meet my boyfriend, whom I had met online...I got a bit of grilling, and they called him on the phone in the airport, but they let me in with a full visa within 15 minutes time.
They ask to see my return ticket everytime, and they have asked to see the money I have with me, and my school ID (that was my main tie home beyond part time work). I think the school ID is what convinced them the most that I'd be going back home. Also, the last time I went was this past Christmas, and it was the first time I'd gone through immigration engaged...I did take off my ring and put it on my right hand instead and said I was visiting my boyfriend (because technically he still is, right?)...they never even asked anything beyond that. It gave me peace of mind at least.
I don't know how to make you not worry. Let me know how if you find out!

Oh, and congrats on getting married!