Relationship Fear

Hello, first I want to thank you for taking the time to read my post. I have been very scared the past few days to get back into an old relationship, not because of abuse or anything of the sort.
When I was with this person, everything was bright, filled with joy, laughter, love, passion, I felt safe with him, we felt loved and agreed we were soulmates. We were inseparable and we both had great relationships with each other’s family. We almost never fought, only a few small little disagreements. But, a few days ago we were watching a movie over the computer (because of quarantine) and he started saying he doesn’t feel okay. I asked him what’s wrong and asked him to pause the movie. He told me he feels like our relationship is falling apart and he feels like he’s hurting me and ruining things. I was shocked and immediately gave him a long message about how much I love him, the qualities I love about him, I talked about how his personality is astonishing, his loving heart, his brilliant mind. At the end of the message I told him, “I’m always here for you”. ... He then took a while, but wrote me a short message, saying, “I’m sorry, I can’t do this anymore. I never lied about loving you. I’m so sorry.” As I was shocked, he left the call and started removing me from places. I was so afraid. I called him crying, and he picked up and was also crying. He told me how sorry he was and how stupid he felt and asked me if I still loved him, I said “of course I do, but why did you leave me?” He said he was scared of ruining things. I told him he didn’t do anything wrong. Then I started to get nauseous and light headed from crying so hard and the fear. I curled up in a ball and I couldn’t talk back to him no matter how many times I opened my mouth and tried, I just felt like I was going to collapse. As he kept calling my name over the phone asking if I was there I tried to text him yes, but he abruptly ended the phone call and messaged me “I can’t. I can’t do this” He then blocked me. None of my messages were going through, I panicked, I choked on my breath, my whole word was spinning and spiraling out of control. I went to another messaging app and called him, he declined. I called him again, missed call. I messaged him to please wait, i said I felt really sick and I’m so sorry. As I noticed he didn’t block me on that app I started to try to comfort him. I said “it’ll be okay, I love you, I’m here, please let me talk.” I called him again, he answered, crying, I was sobbing hard and I couldn’t barely say anything but “why” he said he was scared again, he was sorry, he thought he was hurting me and his depression was telling him “she would be better off without you”.
We were in that phone call for 3 hours, he unblocked me, added me back, he even stayed in the call when he went to work. It only ended when his phone died at his job. After he got off work and drove home, he called me again. This call started at about 11 pm and lasted till 6 am. He cried nonstop, during all those hours, apologizing, explaining, begging. He never cries. He is extremely sorry, I know he is. I told him I love him, but my heart is broken and I’m afraid. He explained he had been keeping things from me, to not stress me out. Family health issues, money problems, stress bottling up. He told me he had a mental breakdown, he was shaking and crying and scared while he gave me that “I can’t” message, both times. He says he regrets it, he wish he had never done. He said he loves me, he still wants to marry me, he still wants to move in together, he still wants to have children and do everything we planned.
I absolutely want everything he wants as well, I still love him more than anything, he’s my everything, and he’s been there for me nonstop. I’ve been there for him nonstop too. He got very sick a few months ago and I nursed him back to health. I got attacked by my ex and he stood up for me and scared them away. I long to be with him, to be where we were before this. But I’m absolutely terrified of him leaving again. Everything happened so quickly. My whole life suddenly flipped and I’m so afraid of opening my heart up again to him. It’s been 3 days since that’s happened, he’s cried with me every night on the phone, he called and texted me nonstop throughout the day. He took a week off of work just to mend my heart back together and be together. But I am so afraid.
Please give me advice. Do mental breakdowns make you do these types of things? Like push people away or snap at them? Make you do things you never would do? I worry so much. What if I didn’t call him, would he have blocked me everywhere if I had given him a little more time? I feel so lost. I constantly feel sick, scared, and I cry rivers. I know that may seem weak, but he’s been there for me ever since we met, I never saw this coming.
I’ve constantly reminded him I love him and I’m here for him, he’s started talking to me about the issues that he’s bottled up and he says he’s feeling so much better. But I’m feeling so broken and scared. I’ve been constantly comforting him and making sure he’s okay, but I’m not okay. I’m so scared, I’m so worried, most of all, I’m so heartbroken.
I would love and appreciate dearly anyone’s opinion on what to do now. Opinions on mental breakdowns, opinions on what to do for my fears and worries, opinions on how to help him express what he’s going through so he doesn’t bottle things up.
Anything will help. Thank you from the bottom of my heart for reading this.
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