Re: Reading Week Trip
Everybody first has sex at a different age, some very young, some much older than you. There is absolutely no shame in not having sex. Likewise there is no shame in having sex if that is what you want.
A down side that I can see with not losing your virginity is that the longer you leave it the bigger the anxiety about it can become. But to be honest it is not worth worrying about, it will happen to you when you either want it to or not.
It is also easy to get into a circle of worry about stds, I know that some can be very bad, but most are very treatable. That is not to say go out there and get some! By being pretty careful you can avoid stds - condoms are essential use, but also if you sleep with someone who is from a low risk category (ie not a drug user, not a prostitute) you reduce the risk considerably. It is a risk, but dont get paranoid.
I also think that maybe you are worrying about what others may think more than you need to. Let them get on with their life, leaving you do do yours. If you really have to defend the reason you are not partying with every chick on your reading trip then these people are not really your friends and you may as well just ignore them. Having said that, dont draw attention to your situation, and dont criticise their activities as this opens you up to criticism back!