OK, first things first, are you sure he's having a wank? If I'm taking my phone into the bathroom, it's because I'm having a shit, not a wank.
Secondly, even if he is masturbating, then that's not necessarily anything tomdo with your sex life. Having a wank and having sex fulfil two different urges, in my case at least. So using wanking as the reason that sex isn't happening, may be stopping you from seeing the real reason that sex isn't happening.
There's been a few time in my life that I've gone off sex in my life. Reasons include:-
Work Stress
An occasion where I couldn't get it up due to alcohol making me get inside my own head too much over the next few months
My partner never initiating, leaving me feeling like a sex pest.
Not finding my partner attractive any more (should have ended the relationship sooner)
Illness (first symptom that I should have paid attention to before I got properly ill)
Aside from the last one, none of the above stopped me masturbating. Sex is a conversation, it involves another person and therefore involves you having to engage your brain. Wanking is the equivalent of sitting in front of the TV, it involves no engagement and you can do it when you have no energy for anything else.
Finally, the phone use is a separate issue. Personally, I don't see the issue with being on my phone while watching a film, but if it's a problem, then talk about it, separately from the sex conversation.