There is a problem that he may feel embarrassed to talk to you. Please take him to a sexologist
or even a counselor and let him discuss his problems regarding performing the sexual act. Today there are a lot of solutions for these problems and unless he opens up no one can help him. So very gently coax him by assuring him that you will be by his side to see this through. If he is unwilling to visit a doctor then you may have to take a call on the future of this relationship. If this marriage has not been consummated, this is ample grounds to pursue a termination of the marriage. Again you may proceed with the utmost caution and care and only if he is absolutely non-cooperative do you need to tell him your decision and choice of action. You can tell him that you want to go about this with the least publicity and therefore his cooperation is essential to proceed in that manner. If there is some other problem, that will definitely come out in this line of action. Please discuss all this in front of the counselor or sexologist as the case proceeds.