Step 1: talk about your feelings with someone you trust. step 2: forget about you two being a couple. Step 3: get use to him as friends. Two tips for this: 1. pray to Jesus, and 2: dont take the next step until you re ready. If you re in the firts step, dont take the seond one until you re ready. and same with the third one. Gby.
The best thing to do is to get out of the relationship since he has feelings for someone else. You can get over him by avoiding contact with him. Take time and do something constructive for yourself. However, it will take time for you to completely forget him.