Feel like I’m losing it, what should I do?

Will power. The best way to get over someone (in my opinion) is to first have a good cry about it, then just start moving on. If things ended in an unsatisfying way and you know that things wont work out, its best that you accept it. Tell yourself that you need no one else to be happy (because this is true! You are the one in control of your own happiness). Take few steps at a time. Try to go out more. Meet up with your friends, volunteer, find new hobbies, go back to old hobbies. Get back to what you used to enjoy before and this time, put your full mind into it and try to enjoy it. Try to remind yourself of how much you enjoyed all that before everything. Try to be happy. If you can put this into test, then it'll work great. Believe me. Good luck!

Strawberry's advice is spot on. I was with my first boyfriend for two years and he broke up with me over the phone. It was unexpected (especially as i'd worked so hard to fix our problems) and I spiralled into depression. I felt similar to what you're describing, and it took about a year or so to fully let go of the pain. You have family and friends around you who will listen and care for you. Good luck!