My boyfriend has a pretty good body (not totally cut, but above average). I am close to the same, but not quite. Right now, I'm 5'6 / 130, which is 10 lbs heavier than I usually am (but he never met me when I was that thin). Is he going to start resenting that I don't work as hard on my body as he does? Do I need to follow his diet and exercise plan to be as perfect as possible so he doesn't get mad that I'm not as great as he is?
I work 5-10 more hours than he does and also have 1.5 hrs of commute time a day, so my schedule is much busier. I'm not just being lazy and taking advantage of him having a great body and mine only being OK.
I am 5'6 125-130 lbds also, and a lot of people treat me like I am real thin! I hate it because I do have some meat on my bones, haha! You are slim though. If you aren't satisfied with your body then work on it for yourself before any one else.
If he really loves you...he won't mind you being 10 lbs heavier than you usually are, It's not like you are fat.