From Excited and looking forward to getting engaged to numb “those feelings gone”

I am in my office crying… I was madly in love with my boyfriend – six months is not a long time but we have the same values, have fun together, and I LOVED being with him. On the Friday I sent my mom an email with people who I would want at my wedding. He has not asked me yet but I was euphoric with anticipation. God loved me – I was finally happy and was going to have my true love and husband and children. Literally out of the blue the very next day, I felt sick and was crippled with anxiety. It was like someone switched off a switch of my feelings for him and I was so sick with anxiety and severe depression that I admitted myself in the hospital (short stay). My psychiatrist put me on 60mg Celexa and am taking an anti anxiety med so I can function. Someone else said they are devastated because the very same thing happened to them. What can we do? I do not want to end my relationship either but am sick with anxiety fear guilt because those “feelings” are gone … or different. God please help us. We are so devastated…. I don’t know what else to do.