Boyfriend rarely mentions anything sexual related. Any ideas why?

So my boyfriend and I have been together for just over a year now, we met in his home country whilst I was living there. Although he wasn't there permanently since he's studying, but we met while he was back there on holiday. We've gone on lots of trips together such as me staying with him for 9 weeks, going on a holiday with his family for 2 weeks, him coming to my home country for a month and other little trips. Soon I will be seeing him in december.

A few weeks ago he was back in his home country doing some work experience and I was in mine, since he was at home with his rents and I still live at home, it's obviously hard to do skype sex or even phone sex especially if there's people downstairs. Yet, he will basically never text me anything sexual related, definitely kissy faces etc but that's about it. I'm not asking this in a way that I'm untrustworthy of him, I mean he calls me for hours during his day that he's free and comes home from lectures and we text all day. But it's just.. because I'm not getting that fulfilled and it feels like we just call to speak about our days/anything else that's happening, I'm not getting that affection/touchy touchy that we all want.

A while ago we had a problem, when we first met, he didn't have much sexual experience and was obsessed with porn. Would download MANY videos, so as a result he couldn't come for quite a while. I looked deeper into it and asked if he used porn, he said he did but didn't think it was an issue. Anyway I found out that while we had that problem, he was downloading porn and it caused a huge argument. I asked if he could masturbate to me and he's only told me once that he actually cummed to some photos of me which I find a little hurtful because if anyone saw my photos, they'd probably be able to easily (don't mean to be arrogant) but I used to be signed with IMG and have a good body. So now he's basically stopped masturbating all together which is not what I have a problem with, it's just the fact he had a problem with cumming and would lie and say he wasn't using porn. Fast forwarding and he told me that he was going to stop all together which I do believe. There was no time when he was doing work experience back in his home country since he would then after work, call me. Now that he's back studying overseas, in his dorm, he's either at lectures, playing frizz or calling me. The other night I asked if he's masturbated recently and he said he couldn't remember and that he hasn't since he last saw me. Then he went on to say that sometimes he will rub himself a bit to a photo. Which then somewhat made me think - I think you are masturbating. Which is fine, but what exactly to, is another question. He was then like "I do think of you sexually and our good times together" and he said he really wants to skype sex/phone sex but thinks that he doesn't want me to get caught since my parents are around.

Last night I said to him that I took a cheeky video but wasn't going to send it to him while he was in a lecture and would send it the next day, meaning today. I've been kind of waiting to see if he remembered and asked where the video is. Then on the phone tonight, I was like "Ohhh I need to send you that video I took (just to see his reaction)" and he was like "Oh yeah baby" then quickly spoke about something different. It's like.. ah, what's the point.

tl;dr: rarely mentions sex over the phone (I'm longing for SOMETHING sexual at least) says he hasn't masturbated since we last saw each other which was in July. He claims he really hasn't even though it doesn't seem plausible by his previous porn collection.