boyfriend rape ptsd

before we were together my boyfriend was raped, in the beginning of our relationship every time we would have sex he couldn’t stay hard for more than a minute. I guess it has something to do with the ptsd of being raped by a girl a few years ago. i really don’t want not having sex to strain our relationship but sex is obviously something I want to do with him but I just wonder if it’s something we can overcome together? Is there anything I can do to fix him?