Dealing with depression. And get over!

I Am very attached to a guy whom I am dating past 4yrs and he has suddenly started behaving very weird and has ignored me and chose to not talk to me i was generally talking to an ex and he started have insecurities about it where I tried explaining and showed him general chats bit he refuses to talk and discuss any of it rather he is avoiding my calls I am very affected with this to the extent that I can cry anytime feel unproductive and dont feel like doing anything i have called him crying angry amd explained to him that how badly i am affected but choses to still not talk he says he needs time and wants me to hold on but my question is time for what and even if I give him time what about my sufferings I have lost my grandfather on 17jan 18 and had expected him to be with me in such tough time but nothing of that sort happened i am suffering partially from a emotional breakdown every now and then and also have trouble sleeping and dont know how to stop talking to him and get over