Boyfriends coworker/friend doesn’t want him to be in a committed relationship with me. How do I deal with this? And should I let the past bother me?

So I’ve been with my boyfriend for 4 years and we have come a long way. At first we both weren’t interested in a relationship. He had a lot going on with his son (problems). Then I just found out that his coworker was influencing his decision about me. He said no longer listens to what his coworker says. I asked if his coworker wanted him to have multiple women. He said no he just doesn’t want him to be committed to me. Never gave me a reason why. Now I’m wondering how many times he spent time with this coworker and he tried getting other women for him. He’s fully committed to me now. So should I just let the past go?
Boyfriends coworker/friend doesn’t want him to be in a committed relationship with me. How do I deal with this? And should I let the past bother me?
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