Hello, and welcome to Just Answer. I will do my best to answer your questions and help with your dog. Have you gone to any training classes with him? Has he been neutered?To answer your questions, no, he can not get you pregnant. His behavior towards you is quite serious and you need to put a stop to it completely before he hurts you or someone else. Training will do the most for you - take him to classes or have an instructor in the home help you gain control of him and have him respond to the commands of sit, down, stay. If he is able to follow these commands at other times, then you need to tighten up the obedience so that he obeys all the time. If he is not neutered, and you are not planning to breed him, then I would suggest neutering him. This will significantly improve his behavior, and reduce his humping behavior.
For the immediate results, you should either place him in a crate when you take a shower so that once you are finished and dressed again, then he is permitted to come out of the crate and less likely to knock you over. This is where some training will also be of benefit.