My son is 17 now and still doesn't say the words "I love you" but I know he does. Knowing he is AS helps to know why he doesn't say the words. Also, once you figure out his Love Language, it makes even more sense. My son's love language is quality time. When we spend time together doing things he enjoys, he knows I love him. That is the way he is wired. When he was younger, and I would spend any time away from him, even if it was shopping, he would feel loved if I brought him home something just for him, even if it was something very small, something he liked. He would know that I thought of him while I was gone, and that told him that I loved him.
When he was about 5 years old, I think, he told me to stop telling him I loved him because he already knew I did and I didn't need to keep telling him. I told him, "sorry, it is a Mom thing and I have to tell you at least once a day. Would that be okay?" He said okay, sort of grudgingly, since in his mind, he had already explained to me that he knew it and didn't need to hear it.
The book: "The Five Love Languages" by Gary Chapman, was very helpful in teaching me about different ways people express love and feel love. I'm not the hugging type either but if you do something for me, I feel so loved. Maybe that is why I could understand my son better than most can.