What does it mean when you sleep with your ex boyfriend?

Well him and me were together for maybe 4 months. It was short but extremely intense. He broke up with me because he thought our age gap was too big (6 years) and he didn't want his parents to be mad at him for dating someone who just turned 18. After the break up we had trouble talking to each other but when we did get intimate soon after he would just say how he missed me and told me that he was really sad after our break up. Which i was to. We kept sleeping together for like 2 months after, then decided we should stop because it didn't help with either of our feelings. He's my best friends brother so i saw him a lot and we had this awkward phase after that so we stopped talking, but when we did talk it would be short and weird. we also couldn't look each other in the eye. He messaged be a month or so ago saying that a show reminded me of him and that i should watch it. And i did love it. we don't talk much since he works weird times but he'll text me up on weekends every so often. then last night i was a little bit tipsy with his sister, who later went to bed so i bothered him in to keeping me company. Then eventually he made him move and that was the first time we've had sex in about 6 months. The odd thing though was that he was making love to me when we didn't even do that when we were dating. Then after he went for a smoke so i tagged a long and all he said was bye i should sleep. SO then we parted ways. He's extremely confusing to begin with, and we have tons of chemistry. He's extremely disciplined, and often holds in his feelings. What do you think this means? thank you