A little more detail would be nice but I'll make due. Talking to co-workers, I wouldn't see a problem but if you don't like him talking to these girls at work, tell him about it. Communication is important in a relationship, so let him know how you feel about what he's doing.
I work with my boyfriend and he talks to the other girls. He sits next to them all day long. Is it normal or am I being overly jealous?
Lack of communication in any relationship is bad, also it's rough to work with someone who you're dating for me, I think it's better to work elsewhere, because this is where problems happen in relationships.
To be jealous because he has routine contact with other females is definitely being overly jealous. If he is doing nothing inappropriate, there is nothing to be 'jealous' of .. If you think you can control him to the point where he can't talk, interact or be in the same room as other females, then perhaps you are just too controlling, and THAT is gonna cause you a LOT of heartache.
I understand why you'd be jealous... But you should just really relax and know you can trust him.. (If you don't feel you can... You're not going to get far in the relationship anyway so...) But relax, try and keep your mind off it and just trust him. Also, talking to him about it and explaining how your feeling really helps.