Just need to talk. No meanies please!

Ok. My husband and I have that disgusting kind of love. Like we always are holding hands and being silly and laughing. We are seriously best friends. We are always amazed how fantastic of a marriage we have after being together 8 years, and married 4. We just have one problem. Sex.
He loves to cuddle more than have sex. He has been tested, and at 26, he does have low testosterone. His first time was with me. He said he came close a few times, but he used to be crazy shy too and just never sealed the deal. When we first started having sex, it was that typical all the time, every room, every position, blah blah blah, then started to taper off.
We'd been married about a year when I brought up my feelings. We have sex about once every week and a half - 2 weeks, and he never seems into it. I'll do outfits, any positions, we have toys, but he just is lazy about it and wants to lay there while I ride him. He always says sex is so much work. As a teen, he discovered porn and I think developed a small problem watching it. It's just easier to sit there and get off rather than have sex.
A few years ago, I got in amazing shape, and when he'd come home from work, I'd be wearing something sexy and surprise him, but I'd just get a small peck, and he'd go to the bathroom then take a shower and want dinner. He's never been good at flirting either, he just doesn't do well with showing affection. 
A few times I've broken down and we fight about it, and once I said 'I get it, you're just not sexually attracted to me!' And he just said yeah. I would say I'm 8/10 things he likes in a woman when it comes to appearance. He just loves black hair (I'm blonde) and he loves tan skin (I'm Irish so that doesn't happen). For a long time, I would go tanning, and hate every minute of it, and I colored my hair, but I hated my appearance with the dark hair. It changed my attitude and I didn't like it at all. But I did it all for him. It's almost like he didn't notice though (guy thing) and if have to point out what tan I did have. 
About a year ago was our last talk about this problem. When he went and got tested for low T. For about 2 weeks this summer, he had a hard time staying hard for sex. He took me to a sex store so we could look at pills and lubes to help him stay hard (didn't work) but he finally got over it. 
He's just so happy in our marriage just being best friends, I feel like all I am sometimes is a buddy who he cuddles. I've told him this, and he tries for about 2 weeks, then it tapers off again and we go back to buddies.
Now for the painful part. I've told him multiple times, I give him permission to sleep with someone else. I feel he may think he settled with me too soon since I was his first, and he didn't get to have more sex before marriage. He keeps telling me he could never do it. He'd feel to shitty, and he loves me to much. He works in a pro sport and travels 38 weeks of the year. He has opportunity. I've told him to go ahead, my only rules are I want to know when you do it. I want to know about her, so I don't walk down the street wondering when I pass a woman if she's the one, don't bring any diseases home, and not in our house.
I had a rough childhood and life before he came along, and he broke me down and made me trust him. But he's not putting any effort into this side of our marriage.
Also, he wanted me to look for an email for him that he didn't know where he put it. I'm more tech-friendly than he is, so I was looking for it, and in his junk mail folders, I found an email from hornyaffairs.com with a username saying he had profile views. I clicked it and it took me right to his profile, very empty, no photos, just his town, age, and the drop downs filled in of his appearance. No messages have ever been sent from his account and only spam ones have been received. I was devastated. I've sat on this info for a few weeks, trying to figure out what to do with it. Then today, his mom thought she accidentally sent a Christmas gift confirmation to his email and asked me to check before he could see. I found it and removed it, but couldn't help it and wanted to see if he had anything incriminating after being away for 5 days. In his junk mail, I found an email from flirthookup.com..... Username was his nickname and his favorite numbers, registered to his email. So I clicked it and the profile was the same as the first, very little info and no activity.
I'm just wondering how many of these he's signed up for now, and I had asked him to be honest and tell me if he was going to do anything. A part of me thinks, ok, he does love porn, and maybe he was curious while browsing and just wanted to see the girls on the sites. 
He's so painfully shy that I really don't think he ever would get the courage to cheat. When I've told him to do it before, he always just says he couldn't do it because he loves our life and marriage too much and it would deviate him to think about hurting me in any way. He's a super softie, so I can see that. And I see it in his face when he tells me these things. 
I just don't know what to do to fix this part of our marriage. I'm running out of ideas. We're in our late 20's, no kids, and rarely have sex.... I'm thinking about finding an intimacy counselor or therapist, but he's so painfully shy, especially when talking about his feelings, I don't know if he'd go for it.