cancer why so Hot then cold?

Hi so i recently started dating a cancer. This is the only cancer I've ever dated, and I'm extremely confused.

We dated for about a month and it seemed like he couldn't get enough of me always calling and Tm and wanting to hangout. In January we both left on vacation which was a little over 3 weeks. He went overseas , but wrote me emails and told me how much he missed me. The day he came back he wrote and said he was on his way and couldn't wait to get back home and to see me.
Well he land... and nothing no call or TM the next day I TM him joking around and asking if he was feeling the jet-lag. He answered back right away "yes a little 🙂" and then nothing.... — He text me 4 hr later "hi" and has made no real effort to see me?? what changed?? He's been back a week and we've talked on the phone once, a few TM back and forth that seem to get left dangling by him. He asked if I was free on friday and then didn't call until 1030 i missed the call cause i was out (ok and a little pissed off), but he never left a message? I know when someone's not interested and all the signs are pointing in that direction i just can't understand how?

any advice would be helpful .