I feel so lonely

I've never felt so lonely in my life. I feel this hole in my heart that the man I'm in love with left. I just want him here but he seems fine with me being gone. I feel like I'll never find anyone. I thought he was the one. Now  he's gone and it feels so strange. I still talk to his mom and it seems like she's taking this harder than he is. All I see on any social media is couples in the amazing relationships. Just seems like everyone around me is in love and happy while my world is stopped. I'm still in shock that people are moving around me while I go in slow motion trying to figure anything out. Now I just feel like guys are trying to use me and get what they want from me because I'm sad and "vulnerable". Idk what to do.