Feeling neglected

My ex and I broke up 6 months ago due to just starting college and after being together for almost a year and a half I felt I needed a break. This hurt him deeply and everyday I regret my decision. Around a month ago we began talking again with the intentions of building the relationship back. Everything was going good, until he most recently lost his mother unexpectedly. Now he lashes out on me randomly and constantly makes me feel like everything is my fault / I’m a terrible person for leaving him in the past. I know he is grieving and I’m trying my hardest to redeem myself and show him this time is very different from the last, but him constantly undermining me and taking his anger out on me is making it hard on me emotionally. What should I do?