If your dad will be upset if he finds out you are on the pill, imagine how bad it will be if he finds out you are pregnant! I suspect that will be the last time you will see your boyfriend. One thing is a fact, keep on having sex without protection and you WILL end up pregnant and you will have to face your parents.
If he loves and cares for you, he should have no problem putting on a condom if you allow sex. You take the risk, he will have to take the responsibility. Explain to him what your father will do to him if he makes you pregnant.
If you can talk to your mom about it, do. Explain to her that you want to be responsible, and that is why you are asking. It is always the best way to handle it. If not, you can get the pill for painful or heavy periods, irregular periods or skin problems (oily, sits and ache)