What advice would you give me about overcoming sexual pressures?

Start by removing yourself from the situation in small ways if you can.

Secondly, Learn yourself, what your lines are in whatever way you feel most comfortable, this will make it easier for you to resist the urge to "just try it" when pressured, which will ruin it for you most likely anyway.

And last remember that, if you aren't completely comfortable with it, it wont be as enjoyable as it could be. Wait until you are comfortable and it's far more worth it.