BF hanging out with his ex

Should I be worried if my boyfriend still hangs out with his ex? They don't hangout alone but she was his first gf and they dated for almost 2 years, it took him a very long time to fully get over her and they still hooked up after they broke up (when they were both in and out of relationships). He still texts her too but I don't read the messages. She also broke up with him.