You can get the morning after pill from your chemist, so that's one worry down, and yes, you will need to see your Dr for the other stuff. Treatment that is sought quickly, will mean quick recovery if you do have anything.
When making decisions, we can all rush in too quickly and get caught up in the moment, because you know this is what you tend to do, try to in the future slow down and think abstractly before reaching a decision. Quickly in your head go through the pros and cons. This takes practise at first and then becomes second nature. It is all learning, not a mistake or stupid or bad decision, it's just a skill you are about to now learn.
I am sure everything will be ok, and I know you will not relax till you have medical results, let us know how you get on, and don't be hard on yourself