How to come to terms with a bereavement I've blocked out and cope with a relationship break down?

You have experienced multiple forms of loss. Between losing a loved one to death and losing a long-term relationship, plus attempts to have it "blocked out," could be complicating your grief reaction even further.  No matter how much you may try to "block" your grief, it inevitably resurfaces. Moreover, it seems like you are not able to effectively mourn the loss of this relationship if your ex remains tethered to you in an intermittent capacity, no less as he appears to also block you on occasion.

When a relationship ends, you grieve the loss of what you had hoped for y'alls future together, routine, family, normalcy, traditions, extended family, etc.  Feeling down and confused after a loss is completely understandable. Your relationship ending and a death of a loved one both took heavy emotional tolls on you, no matter how much you may attempt to avoid dealing with these losses. Even if it was not a healthy relationship,  it is still a loss nonetheless. Grieving a relationship loss can resemble the stages of grief - denial,  anger, bargaining,  depression, and acceptance - we typically find in the loss of someone's life. A typical grief reaction is anywhere from six months to a year depending on several different factors.

You already started the healing process by merely breaking the silence. It is not easy to navigate the devastating effects of a breakup and death. Reaching out for help is certainly no easy feat either. But the good news is that you have shown a heap of courage when you submitted your question to us on BetterHelp. Now you no longer have to bear the burden of the emotional pain you have endured for so long in isolation. Healing requires time and work. We cannot rush either - especially the former. 

I encourage you to instead invest your emotional energy in taking care of yourself - speaking kindly to yourself, eating well, moving your body, hanging out with people who make you feel good, etc. Working with a therapist can help you reach the goal of moving past your ex and working through your grief of the decedent, but more importantly, finding new ways to cope and heal from this loss so that you can recover fully from this loss and move forward in your life towards the new possibilities that await you.