I am in love with a man who is committed with another girl. What shall I do?

Hi doctor,

I am a 25-year-old female. My manager is a very good friend of mine. We are good friends for one year now. He is 33 years old. He is very sophisticated in nature, very clean and modern yet a bit conservative. He likes girls to be calm, a little conservative, patient, sweet, and lovely. He is impatient. He was in love with a girl but now she got married to some other person. He tried a lot to convince her not to marry. He wanted her to be with him like living together yet he was fine even if they do not get married. But, she got married. After her marriage, the guy with whom she got married was not too interested in her. So, she is still in touch with my manager. They planned to buy lands, etc., when they were committed and already had bought a few. I have seen him messaging her. Whenever her message comes, no matter what he is doing, he stops the work and responds to her. When she got married, he was extremely disappointed and even cried. I have started falling in love with him. But, I never told him. I would say our relationship is very cute. After work around 10 PM, we always go to the airport in his car to have coffee. We are doing this for the past nine to ten months. He likes my voice, the way I speak, my smile, and mostly my expressions. I behave like a kid in front of him and I love poking him. I feel the utmost comfort with him. He shares everything with me except whatever he talks to his girlfriend and his financial status. He works hard but all the time he remains stressed. He used to be happy last year when he was with his girlfriend. After her marriage, he became too distressed. He hardly sleeps well. One day he kissed me. I too did. We started doing this regularly. When I asked him the reason, he said he does not know, but definitely, it is not right. He told he might be having gratitude towards her. He was clueless. We still repeated after that. At times, I see some love in his eyes. At times, I do not see anything for me. In fact, he also told me he wants to sleep with me. But, after some days he told he will not do that. He is still in touch with the other girl and I did not know what they talk. He is a person who does not talk too much and is introverted. I am always the person who asks for coffee to him. If I did not ask he will also remain the same. If I did not message, he will remain silent. But, whenever he has some problem he approaches me. Now, I love him. I am not sure whether he loves me or that girl. I am in a very confused state. I do not want to propose to him now and spoil my professional relationship. I do not want to marry anyone else. I am in a dilemma now. Does he love me? If not, then why he kissed me? He is not the kind of person who will hook up with a girl just to kiss. If he loves me, he may not marry me. What should I do then? My family will definitely love to see me getting married. Please help me.