Advice! My bf wants to move out but us stay together

So My SO has been dealing with severe depression for the last couple months. I also am bipolar with severe anxiety. I have tried to be supportive and be there for him. The last 2 months have been especially rough since I found out that my right tube is completely blocked and I won’t be able to have children without help. He has not been there for me at all which ok I get it your dealing with your own stuff. So he’s been seeing a counselor and dropped on me Sunday night that he wants to move out and be on his own for awhile to get himself right. I say all the right things ( you need to do what makes you happy, I just want you to be happy etc...) so he’s been telling me how I’m the only thing that makes him happy and that we’ll be ok and it’s not forever. All I can think is if I’m the only thing that makes you happy why are you leaving me? I’ve had a pretty crappy life and he was the first person to ever believe in me and love me for me. So naturally my depression and anxiety comes crashing in with all the insecurities and stupid shit that it does. I can’t help but be negative about it all and I’m really trying not to be. I just need some feedback. My mom and a couple friends say it could be a good thing. That we’ll reconnect and he’ll miss me but of course I’m over here all depressed like ummm no this is stupid. Sorry so long and all over the place just need to let it out and get some feedback from you ladies TIA