I welcome you with open arms and a warm smile. I must say, what a beautiful person you are, to be so concerned about your partner, yourself and the health of your relationship. Yes, when one person in a relationship suffers from depression, it is typical that both members end up suffering in their own way. I experienced depression for some years, before eventually coming out of it, which certainly tested my husband's devotion and endurance. He's one seriously tough cookie, which explains why why we're still together.
What you are experiencing (a sense of loneliness, disconnection or lack of affection, negativity, cruel talk etc) your partner is also experiencing in his own head. That cruel self-talk can certainly be torturous. Whilst love, unity and energy or a sense of drive are expressions of the soul, they are also expressions of the chemistry surging around up there in our head. If the chemistry is off, this will often be expressed through our words, actions and sometimes our over all health. Having been both inside and outside of depression, it definitely is like being a whole different person.
Some folk can be quite proud, believing that if they admit they have a problem they are admitting to failing at life in some way. Deny the problem, deny the sense of failure. Sometimes, it's not until people hit rock bottom that they admit they have a problem they are unable to deal with on their own. By the way, the only real failure present in depression is that which involves neglecting to take the first step on a path to recovery. If your partner does feel as though admitting to needing help is like admitting he's 'a failure', this may explain why he perhaps resents your constructive advice in regard to seeing someone. Passive steps might have more of an impact, in his case. Wondering if he might be a little more open to reading literature on depression (the facts) or perhaps there's a way to persuade him to get onto the forums here, where he can remain anonymous. With depression being a lonely experience, to get support from people who he can relate to might provide some turning point for him, in getting help. Just reading what others say and not writing anything himself could be a start.
It's important you continue to seek support too Coraline08. For you to avoid being pulled into a depression (that dark place) stay in the light, by enlightening yourself through education regarding this form of mental dis-ease.
Take great care of yourself