deployment struggle

my boyfriend is in the army and deployed right now. he's been gone going on 2 months now and he's slipped into a horrible depression (only way for me to describe it). I've been supportive as possible and just letting him sleep when he gets off and not expecting him to give me attention (he works 15-18 hour days over there so I understand he's exhausted 100%). He stopped calling me baby/babe/etc. and being sweet and I asked why just to see what was up and he said he's not sure if he's ready for long term when we've been together a while now. there's more background but this is the jist of it. I guess I'm wondering if there's other couples out there who's s/o questioned y'alls relationship and if it's because he is so tired and sleep deprivation is getting to him and ways I can support him. I watch what I say and how I say It and reassure him I'm here for him. I'm just feeling discouraged. (please no rude comments, I feel like we are all here for support and if it's not helpful please don't say it)