Why is it so hard?

Why can’t I get over something I never really had. I was seeing this guy for 3 months and we were working toward a relationship we met one day at the end of a trip I went on and then we’re getting to know each other long distance. We honestly acted like we were in a relationship, he came to visit me multiple times in those three months, met my family, bought me a grad gift and Christmas gift. Word for word told me “IM NOT GOING ANYWHERE. Okay? I hope you believe me because I'm not the kind of guy to do this for this long just to break your heart”. Then his ex texted him and they started to talk again and he disappeared like he never cares about me. He told me he needed time to be single and spend time with his family and work through some stuff. I’m having a really hard time getting over it with everything he told me, he promised me. I was so ready for a relationship and still want to be in a relationship with someone but how do I trust someone else again, I have never had my heart so broken or someone made me feel so so worthless.