I had something similar happen, and I won't lie to you or sugar coat things; you are going to be hurting for a while. This is one of those situations where everything you see is going to remind you of her and cause you a great deal of grief. The best thing you can do right now is ensure that you don't see her anymore by removing her from any and all social media, deleting/blocking her number, etc.
Jealousy can be a real bitch, believe me I know.. You're in the woods now, and things look bleak, but you'll find the road soon and get back to some sense of normal. It probably won't be any time soon, but you can at least take solace that this didn't happen on a holiday.
Keep yourself busy, talk to friends, and get outside whenever you can. You'll be surprised how much getting a bit of fresh air can help your mood.