20 something, trying to lose!

HI guys, I am 22 and still in college(graduating in May). During the week i find myself sticking to my diet really well, then on the weekend I go out with my friends or Boyfriend. I can control my eating until i start drinking. How can I tell people i do not want to drink, without seeming like the party pooper. Or what are some options that i can just sip on or only have one. This is my biggest struggle! Help

I have this same problem with wanting to drink when we all go out and one thing that helps is saying that I have to drive somewhere, If they are decent people they should understand that you don't want to kill someone by drinking and driving. another thing you could do if you do want to enjoy a drink is have a vodka diet sprite/7up. vodka only has 87 calories per shot so if you can stick to that and only have one or even two you are still under two hundred calories. (hint: make them tall and put less ice in and more pop and they last alot longer to just sip on, also don't use a straw, you drink it faster then if you just sip off the rim of the glass)