Update: They went of for a coffee together alone when he knew I couldn't remotely be there because I was busy.
Also, his ex now calls more frequently, plus, they went out at about 16:00, my boyfriend had had no sleep the other day so it was expected from him to sleep early that day so he slept from 21:00 but woke up at 11:00 in the morning (14 hours of sleep) plus he also felt sleepy for the rest of the day.
With the combination of his ex's frequent calls, I couldn't help but wonder, did he cheat on me with his ex that day? Met at 16:00, slept at 21:00, 14 hours of sleep. There is a gap there isn't there? Also, they went for a coffee very near his house. Which is strange. I don't know.