How do I (27F) tell bf (31M) how his sneaky midnight indulgence is affecting my sleep?

I am in an LDR relationship with this guy since a couple of months and we recently started living together at his place (I’m in his country for the next few months). For many nights in a row now, I have been woken up by movements under the blanket and on the (really shitty) mattress, which coupled with the changes in his breathing and other various sounds, have led me to believe is him masturbating. I honestly don’t mind if my partner chooses to engage in some solo time without me. However this is getting seriously uncomfortable. I am not able to get quality sleep at all – waking up 2-3 times in one night to the fapping sounds and the movements and the heavy breathing. Apart from the lack of sleep there’s this mental and physical discomfort of lying next to someone who is vigorously masturbating every night not knowing I am awake… a discomfort that increases until I sit up on the bed and he stops doing it out of fear of being found out. I feel weird trying to talk about it with him, like a general awkwardness and a lack of idea on how to approach the topic, especially because he’s doing it under covers (literally). I really need to fix my sleep as it as begun to affect my waking hours. Appreciate any help and perspective.