My boyfriend and I used to have an extremely healthy sex life but because of a serious test he's studying for he doesn't ever seem to want to, should I just be patient?

Be patient . If u care about him of course u need to be patient . After all if u have a serious relationship passing his test is for the benefit of both of u.
Yes. Your patience really will be rewarded. Just let him know that you understand he needs to be successful in his studies and that you are there to give him some time to take a break and recharge his batteries and yours so he can be even more successful. Good luck!