Is it permissible for a man who is suffering from some sexual difficulties to get married?

Praise be to Allah.

The nature of human beings is that there are great differences among them with regard to sexual desire. Some of them have strong desires, some have less than that, to a greater or lesser extent, and there are some who have no desire at all. If you have any desire at all, even if it is little, then you may get married; it is sufficient for you to be able to have intercourse, even if it is only once every month or every two months. 

Fatwa of Shaykh Ibn Jibreen, from Fataawa Islamiyyah, vol. 3, p. 161. 

But if there is a complete inability to have intercourse, then that must be made clear to the guardian of the woman before the marriage takes place. And Allaah knows best.