Performance in a Man

My boyfriend has a lot of trouble becoming aroused when we are about to have sex. He claims it is not me and he loves me but he comes up with various excuses for his inability. These include, hes use to watching porn all the time, he doesn't want to just have sex with me for pleasure, hes tired, hungry, stressed, or nervous because he was a virgin before me. However, we have such a strong relationship and I don't understand why this is happening? Can you please tell me why? Does he need to see a psychologist? Also, he was sexually molested as a child... could this be it? He claims it is not the reason.