I can understand not enjoying watching him masturbate, but try to get past feeling any resentment or distress regarding his masturbation. It's perfectly normal for men (&women!) to masturbate even with a healthy sex life. In fact, and I hate to state this without stating the source, but years ago I read a statistic that there is often a direct correlation between masturbation and a healthy sex life.
At your age, I would probably have felt uncomfortable watching my bf jack off and may have even felt jealous or inadequate. But now (and I'm with the same guy as I was back then) I think it's crazy hot to watch him. AND we have learned quite a lot about pleasing each other by watching each other masturbate.
I know it's silly to get upset over it, but I still feel terrible when he does it.
Yeah, maybe we will end up getting more comfortable with watching each other masturbate later on, but right now he said that it's boring watching me, and I just get upset if I watch him. Although I have learned a lot about giving better handjobs and blowjobs from him telling me how he masturbates. P:

