sweetie - just an expression
if can manange some time to go out - seems not a date, just go out for something together
suggestion - imply that you already have BF and he would be one of your best friends
nothing more, hope can be help :)imply：对外国人imply还挺考验语言分寸的，如果人家本无它意，他们不会觉得impolite吧，外国人本来就挺好交际的。。。when he asking you what a u doing? you got the chance, just say dating with your BF