"Issue" #1

>My boyfriend doesn’t care that my coworker seems interested in me

This in it of itself is not a problem. It's not your bf's job to shut down your coworker. That's your job, and your bf seems to trust that either your coworker isn't "romantically" interested in you or that you'll shut him down if he does show that he's "romantically" interested in you. So honestly no problem here as far as I can see.

Issue #2

Literally everything about this reply here ^

You and your bf should be spending quality time together. Everyone is allowed and should have "alone" time to do their own thing, but if he's not giving you any of his time that's an issue.

>Now, I have a guy who actually does want to do stuff with me and takes an interest in my interests. I don’t know. I’d just think maybe my boyfriend would try to step it up if he really cared I guess.

OOF... Sounds like you're having "the grass is always greener on the other side" trope. Not really fair to be telling bf about this guy and expecting him to see that you're really asking him to spend more time with you.

>I’ve expressed to my boyfriend before that I often feel very lonely with him. He doesn’t have much to do with me and shows little interest in me. He never likes to go out and do things with me.

Not sure what "I've expressed" looks like, but I'd recommend a serious sit down convo with your bf about this. He needs to be spending more time with you, otherwise, are you still with him?

>he said yeah, because now he doesn’t have to.

If that's what your bf told you, he's either an asshole and you should seriously consider dumping him, or he's a dumbass and, assuming you want to stay with him, should educate him on what a relationship is.