Long story short, I got in touch innocently with an ex on Monday. We ended up messaging each other all through the night and didnt stop until 9am Tuesday morning. He remembered so much about our relationship that I'd forgotten about. I was his first girlfriend and sexual partner. He said he would message when I finished work at 5pm but didnt get in touch till 10pm saying he'd been busy. He then took a phone call from his brother for an hour and messaged once to apologise then fell asleep. He messaged yesterday but was  as if he was a totally different person. I'm really upset by his behaviour but not sure if I've got wires crossed. The first night all the old feelings were there and there was definitely a connection. Should I persevere or give up?