Just take the time and talk
There are so many factors in not sleeping with your girlfriend 1 could be maybe he is trying to see if there is more to the relationship than just sex. 2 maybe he jacks off too much and can't get it up. 3 maybe he is seeing someone else 4 maybe he doesn't feel hot. These are some things that can factor in no sex you have to ask yourself do you guys have good conversasion and enjoy spending time together? If the answer is yes then you got you a #1 if the answer is no then the rest of the #'s might apply