HI
I have also been in your situation and be careful not to do anything to quickly - as it is part of the illness, I agree with the other comments posted here. Our illness is always looking for better, when it could be looking right at you.
Relationships are hard for both parties - and more so in our situations.
You need to ask yourself:
Does your partner love you for who you are - and you love them?
Do you have fun together?
Does your partner support you with depression? - this is a very big part of someone that suffers with depression - getting support from loved ones.
I was in the same boat as you but I left the relationship and it was the biggest mistake I made and still regret it today, but pride and being stubborn got in the way and I wish it hadn't. I had a great partner who loved me and supported me through my low days and would have done anything for me, and now I'm on my own. Be careful that you don't end up lonely!! It's not a nice place to be.
'Ex' is an ex for a reason - it didn't work the first time, so the chances of it working again are slim!! Be careful not to ruin what you already have! And avoid contact with the ex - as they could be playing games with you.
With depression our minds try to make us believe things and can lead us down the wrong path. Be strong and do the right thing, but ensure it's not because you are feeling low and you make the wrong decision.