I’m confused can I please have some advice?

I feel so sad and confused. I met a guy who was so nice and sweet. He was so respectful and kind to me. He wasn’t perfect but he seemed to be a pretty great guy. We eventually got into a relationship. This last month has gotten me so confused by his sudden changed behaviour. He went away for work and it was his birthday. I said can we video call after you land and he said yes. I had a cupcake and candle and I was going to sing happy birthday to him. 1 hour has gone passed and I texted him what was going on and he said I’m having dinner with workmates can we chat later? Which upset me but I didn’t say anything to him. We were hardly talking while he was away and I even said to him do you even want to be with me? He said he does but work has just been so busy. A few days go past and we talked on the phone and told me he misses and can’t wait to go home to see me. I was going through a hard time too because my mum was having surgery a few days later to remove cancer and he knew I was sad and worried about my mum. Two days later after telling me he misses me I get a text at midnight telling me we shouldn’t see each anymore because work is going to be busy for the next few months and he will be away a lot. I then try to call him after him telling me that. He responds with I will call you tomorrow I’m going to sleep in which he didn’t call me the next day. I asked him could we talk about it when you get back and he said yes. I asked him do you still miss me and he said he always does. Sometimes he would say he doesn’t know. We were suppose to meet up but he changed his mind and didn’t keep his word. It was like he was just playing mind games with me. After he broke his word I stopped texting him. I was just keeping in contact because I thought we were going to meet up to talk about it like he said he would. What broke my heart too is he knew I had his birthday presents waiting for him which I got rid of now but he just didn’t care. I don’t understand how he could be so cruel to me. I always showed him respect and the thing is he was so kind and respectful to me in the beginning too. He was encouraging, supportive and he made me feel beautiful. How does someone just change like that? Especially when I literally did nothing to him. I give him his space, I’m not clingy, I genuinely cared about him and I’m just so hurt and confused by this.